In the dark ruins of Fuyuki city, sounds of thuds and hits clashing can be heard on a road in the town nearby. This was Kamen Rider Singularity punching every Gurongi who stood in his way of protecting his companions and also to get him back home. He was flowing with the immense power of the dragon that angers him to those who harm his companions and friends.

He dislocated one of the bones of the Gurongi trying to sneak up behind him before knocking him back to his friends. The Gurongis are feeling the cold crawling to their skin as they try to intimidate him but his intimidation is much stronger than them. He spinning kicks them with his legs flowing with the power of the dragon's aura which formed the dragon's hind legs and behind them is the dragon's tail.

The kicks hit the targets so they were all pushed back and exploded in fiery flames of his power. Mash was speechless and Fou could only bark awe from his fight. Mash mutters his title almost as if she felt familiar when she hears this word.

Mash: Kamen... Rider...

He then faces Mash as he asks her the first thing he saw in her when he met her in his frail human state. The armor resembles her knighthood and a giant shield that for some reason she can carry around so easily.

Player: Mash, are you... fond of me? What's with that color of your gear?

Mash blushes a little but realizes what he meant by the way she looks at her.

Mash: This is...

But suddenly a scream a girl is nearby meaning someone is in this city and a survivor. They look to where it came from and it's just in the center of the hellfire of the city. He was about to move out to help when Mash suddenly asked like she's his master, which at this point he is.

Mash: Master, your commands. You and I will get through this situation together, Senpai!

He then looked at his right hand which the armor lets him see the Command Seal. It was a motif of a shield mixed with a dragon's motif. More likely his progrisekey's SP symbol. He looks at Mash before he gives an obvious order.

Player: What else? We go there and save the damsel in distress. Come along!

He began running towards the center of the battle and Mash followed up but was surprised by his impression towards her. Clearly, he should be ordering her like she's a literal servant of the king. But he has that blunt impression of getting the gist and straight to the point.

In the center of the chaos happening in the city sounds of footsteps and the rapid breath of exhaustion of a woman. She ran away from the crackling bones of multiple skeletal enemies wielding weapons targeting her. It was the Director of Chaldea, Olga Marie Animusphere.

She was having trouble running away from them due to their insane stamina unlike hers. But she trips over when she's just looking behind her and the downside is that she was sprinting on heels. Instead of running away, she fires her magic but it only kills one enemy, which the enemies find funny as they laugh creepily and continue to run toward her.

She just keeps firing her magic toward the enemies but their numbers are too great for her single-target magic attack. She then complains about her stressful and intense situation.

Olga: Why do these kinds of things always happen to me?!

But suddenly she heard a lightbulb breaking beside her and when she looked up it was another skeleton enemy about to kill her from above. She fires her magic attack but it ends up missing because it dodged the attack. She closes her eyes and hopefully, someone saves her.

Olga: Help me, Lev!

But her demise didn't come as she heard a loud metal collide with the skeleton's sword. When she looked towards her it was Mash who easily smashed the skeleton with the blunt edge of her shield. She was confused when she saw her different look.

Olga: Mash?

She continues attacking the enemies with her shield, blocking their attacks and retaliating with her counterattacks. She was so confused about what was happening that she didn't notice the incoming enemies beside her. She only looked beside her when she heard growling and she looked up to see the terrifying three Leopard Gurongis with one of them about to pounce her.

But instead, the Gurongi met a boot to the face and a kick to its side rolling its way back to its fellow friends. She looked to see Player in his Rider form as he taunted the Gurongis.

Player: Sorry guys, but you just made yourselves the nails in your coffins!

He fights the Gurongi as he punches the Leopard to the chest and tosses over the other Gurongi when it tries to front-kick him if he doesn't catch its leg. He proceeds to kill them with his fire-coated fists but one of them tries to escape if he doesn't grab its hair and then he asks Olga while taking hold of the last Gurongi.

Player: You okay, Director?

He then pulls the leopard towards him and kicks him to the crotch and a kick to its face, killing the last Gurongi ambushing Olga. He still sees the look on her face and realizes it. So he just disables his transformation and looks at her with a poker face look. 

Olga: You!

Meanwhile, Mash wraps up her battle when she smashes the last skeleton with her shield creating a small crater due to her powerful abilities. She meets up with Player and Olga to see if their okay.

Mash: Are you hurt anywhere, Director?

Olga: Okay, what is going on? Where are we?

Mash: This is Singularity F. Fuyuki, 2004.

Player: 'The timeline between Fate/Zero and Fate/Stay night...'

Mash: It may be hard to believe, but I-

Olga: You're a Demi-Servant, right? I could tell just by looking at you. What I want to know is, why didn't it succeed until now?

Player: 'Oh you have no idea how it was done...'

He wanted to keep a secret of how it happened because it would make her stressed even more and demand more answers, or in worse cases she would be tormented by it. Mash says the history of their summonings but leaves out the crucial detail of how it was done.

Mash: I'm sure you know that Chaldea prepared a Servant beforehand to resolve the investigation of Singularity F.

She remembered a memory before she rayshifted with him, she looked up to see somebody in front of her. A ghostly man who offered his hand in front of her. A sign of contracting with him, and she sees another person behind him but can't make out who it is due to its dark ghostly aura. But one thing she notices is that it has a neon gold outline on his aura.

Mash: Right before I almost died, he offered me a contract. In exchange for giving me the abilities of a Heroic Spirit and Noble Phantasm, he wanted to eliminate the cause of the Singularity. So I merged with the Servant to become a Demi-Servant.

Olga: Then this substitute commoner has become your Master?

Player: It's not if he can fight on the frontlines too. *snaps a photo*

He pictures both girls which startles them but Mash blushes a little when she sees it but for Olga, she is irritated by his impression.

Olga: Excuse me, a Master fighting in the frontlines?! That is absolutely-!

Player: If you're gonna say about violating the rules of the Mage Association; To their existence, I say no thank you!

He didn't acknowledge the Mage Association caused Olga's reality to be shattered in a worse way. He was pushing his buttons too far even though he didn't care. Her anger rose more and more until it almost reached its peak when a call on his bracelet emitted and he pressed the button. This allows for the communications of Chaldea to be in operation once again, and in the process, they met with a familiar face back from the base.

Romani: I finally got through! Hello, can you hear me?

Player: Hey, Roman, we're here.

Romani: Player, Mash. So you did get caught up in that rayshift. Without being in a Coffin, you had to withstand the consciousness you have right now. But what's with that costume of yours, Player?!

Player: Never mind that for now. Because someone's here with us who is also caught up in the rayshift.

He and Mash get out of the way to show Olga sitting on rubble looking at Romani and she asks him. He was shocked to see her alive and well.

Olga: Why have you taken control, Romani?

Romani: D-Director! You're alive?!

Olga: What are you talking about? Why is the head of the medical section in that chair? Where's Lev?

Romani: Professor Lev was right in the middle of that explosion. I can't see any hope of his survival.

Olga: No...

Olga is surprised to hear this as Romani tells the sad news to everyone. But for Player, knows the feeling of somebody who angers him so much will not die that easily.

Romani: The reason I've been entrusted with operational command is because there isn't anyone left who outranks me.

Olga: Then what about the Master potentials? What happened to the 49 people who were in the Coffins?!

Romani: Unfortunately, all of them are in critical condition. At this rate-

Olga: Don't be so foolish! Transfer them to cryopreservation immediately! Our top priority is to ensure their survival!

Romani has seen her authoritative tone and immediately straightens himself.

Romani: Will do!

Romani leaves the call to do her order while Mash and Player look at her.

Mash: Director...

Olga: As long as they don't die, this can all be justified later. I can't possibly carry the burden of 49 lives on my back.

Player: You're not alone on that one.

Olga looked at Player with an incredulous look as the glare of his visor mixed with his voice signifies his steel will to carry out and fight to survive and finish the mission to get him back home.

Player: We all three are carrying their burdens now. So regardless of the complaints we have to carry it. We'll find the one responsible for everything that happened in the facility.

Romani comes back online as inside their HQ, the staff is being treated by the medics while working.

Romani: Currently, Chaldea has lost 80% of all functions. Once communications with the outside are restored, I'll request supplies and start reconstructing Chaldea. That's the status.

Olga: Fine, Romani Archaman. I'm not happy about it, but until I get back, you're in charge of Chaldea.

Romani: Roger. But still, a Demi-Sevant, a fusion of a Heroic Spirit and a human. I can't believe it succeeded at a time like this. There's also the question of the project Outsiders 2.

Olga looked at the Kamen Rider with intent and likely knows something related to Project Outsiders 2. It was the 2nd project sequel to the first Project Outsiders which ended up with unsatisfactory and selfish results. But regardless she looked at Romani to seal the deal between him and Mash.

Olga: Well then, starting now, both Player and Mash Kyrielight will begin an investigation on Singularity F.

Romani: Then I wish you all luck. If an emergency comes up, please contact me.

Olga: Hmph. We can send an SOS, but nobody will come to save us.

Romani wants to comment but he just facepalms before ending the call. Mash and Player talk to her as Mash asks a question.

Mash: Director, are you sure about this? We could wait here for help instead.

Olga: After this incident, I can imagine how much protest we'll get from the Association. We can't go home empty-handed. Sorry, but you'll have to help me. Mash and Player.

Mash: Roger!

Player: I get the gist of it.

Olga: Gggh!!! *sighs* I never thought the day would come when I'd have to rely on somebody like you.

But suddenly they got a call from Romani once again. Olga was annoyed, but when Player saw Romani's face, it looked serious.

Olga: You're being annoying! What do you-!

Romani: Please get away from there right now!

Mash senses it too as she advises everyone.

Mash: I'm detecting signs of an enemy nearby! This is... a Servant!

But as he focuses his senses even further he can hear the sounds close by and then a familiar sound rings in his ear like a tinnitus. He was shocked by what this was as he looked at his surroundings and saw a glass nearby. He shouted to the girls before pushing them away from the glass beside them.

Player: Get away!

As he pushed them out of the way, they yelped in shock. Then a massive monster emerged from the glass, a giant purple cobra snake hissing and slithering around him. He was surprised by the fact that the VenoSnaker was here in this place.

Player: Ouja's mirror monster... Mash, Olga, I'll lure it away from you! Go on ahead!

Olga: What the hell?! Are you crazy?! You can't fight that thing alone!

Player: Trust me for once, Olga! Mash, it's an order, go!

Mash: Director, let's get out of here!

Olga: What about him?!

Mash: I believe he'll make it out alive! Because he always has!

The player and Venosnaker are the only ones in the vicinity as he looks at the snake with determination.

Player: You want me?! *activates his progrise key*

CHAOS

Player: Come and get me!

AUTHORIZE

PROGRISE

MASTER AND BREAKTHROUGH HISTORY

PURGING DRAGON

The Rider who breaks fate and masters all.

He transforms into Kamen Rider Singularity as the chase started with the Venosnaker trying to catch him as he runs away. Meanwhile, Mash and Olga are running away and find themselves in a nearby river. They hear the crashing of buildings and the hissing sounds of the contract monster nearby.

Both girls cannot lie, they're worried for his safety. Mash was worried to a certain degree, but Olga was the most worried. This is because of what she read about the Venosnaker being part of Outsiders, except it was in its evolved form.

They carefully stay on guard of their position while they wait for him. They continued hearing the sounds of multiple distortions nearby meaning he was close by. Mash suddenly saw his reflection in the river so she called out to him.

Mash: Master!

When he emerges from the water's reflection, his suit is wet. So, he shrugs off the dirt and lets it dry with his intense heat-radiating armor. Olga then asks him about his knowledge of what happened in this place.

Olga: Hey, commoner. Do you have any knowledge of this place at all?

Player: Well, the brief version is that it's like the original Holy Grail War. 7 Masters, 7 Servants. They activate it and battle it out to death to determine the winner. But then someone sabotaged it and disrupted the timeline. Now the end question is, who wins? Did somebody win or there was no winner at all?

Fou: Fou, fou!!

Fou barked as they stumbled upon a barrier blocking their way. Mash and Olga are trying to observe and identify what this is. But then Y/n decided to test it when he saw something on the ground, so he grabbed a stone of a hand and threw it towards it much to Olga's shock.

Olga: Wait!

Mash: Master!

As the object was about to collide with the chain, it suddenly started moving towards it, capturing the stone before crushing it to a bloody pulp. Olga was surprised to see his keen intuition. He then started talking strangely about whoever was stalking them.

Player: Come out! I know you're watching us this whole time! Your chains gave it away!

???: Too bad. The fresh prey got away with my chains.

It was then revealed itself after turning herself visible from her invisibility. It was a woman with a black hoodie cloak, wielding a scythe, and had purple hair. He recognizes her as he looks towards her face, the face of someone dominating and ready to devour anybody who gets in her way. They put their guard up especially Mash after putting herself in front of Olga and beside her Master.

Medusa: An unknown Servant and an unknown Master. Ah~, how young and fresh...

Mash: A servant! But I don't see her Master-

Player: I found him...

He pointed towards the person who was also turned into stone. It was a young man with curly hair and an expression of screaming for his dear life before he was turned into a stone. She proved it further when she claws her sharp nails to its stoned face.

Olga: This world has gone mad so a Servant without a Master is not surprising.

Player: One thing I'm confused about is why did you this when you have a choice to let go of everything.

Medusa: You complain? When you wander into my hunting ground, I'm free to treat you however I please, am I not?!

She immediately decapitates her former Master without hesitation. The two girls were disturbed by this action. But he's still thinking of how she looks familiar.

Medusa: But don't worry, I've lost one station, but now I'm going to have three new ones.

She licked the blood off her face with her snake-like tongue as she looked venomously at them. Mash sees no other options on this as they cannot skip this ahead. Medusa was already a problem that needed to be dealt with immediately.

Mash: Our only option is to fight.

Olga: Can you take her on?

Mash: Yes.

Medusa: Oh, how bold. How fresh. Is this your first time fighting as a Servant? Then as your Senpai, I'll teach you and this will be my first lesson and your last.

Medusa suddenly erupts a massive aura that makes everyone except for him flinch. She looked at them with a psychotic expression on her face. She then pulled out something from her waist, he was shocked by what she pulled out like his prediction was right in a worse way. A card deck with a cobra snake motif.

Player: That deck! Your-!

Medusa: Oh? The Master knows what this is... I'm so happy! I'm so happy and vexed right now I want to devour all of your flesh after I'm done with your servant!

Medusa points the deck towards her scythe's blade which creates a reflection and summons a V Buckle belt out of nowhere. She laughs like a psychopath as she stabs her scythe to the ground motions her right arm pulls her left arm back and starts to say the word with her right arm motioning like a snake's quick bite.

Medusa: Henshin!!

She inserted the card deck into her belt as the sounds of energy forming around the mirrors formed and came towards her in three different directions. They all merged and formed her into the cobra medieval knight and grabbed her scythe which now turned into a snake-shaped scepter known as Venovisor. She became a Kamen Rider which resonates with this Kamen Rider's violentic personality.

Player: Kamen Rider... Ouja.

Medusa: Be careful of what you say and do. *picks a card* For once the word "fight" passes your lips, it has already begun.

Sword Vent

Then a blade resembling a cobra's tail appeared on the bottom of the scepter, she twirled it around and started attacking her by disappearing first. Mash was shocked she disappeared but then she appeared and started attacking her. She strikes the shield and it creates a shockwave that causes Mash to be pushed back a little.

Medusa: You're desperate. Excellent. But be careful. My lance is the Lance of Immortal Killing. Any wound this lance delivers cannot be healed by any means. Even if by some miracle you could completely heal your entire body. Do you understand? If you make the slightest error, you'll be a failure of a Servant for the rest of your life!!

Mash: Kh!

Medusa: HAAAAA- oof!

Medusa was suddenly kicked away from Mash and she looked up to see him blocking Mash's way with his arm. She was slowly getting exhausted due to how powerful Medusa had become after becoming a Kamen Rider. He looks at her in worry he asks if she's okay.

Player: You okay?

Mash: I'm good, Master. Her power is crazier than I thought.

Player: Considering she becomes a Rider that has the same personality as her it would only make sense.

Mash: What is the plan?

Player: We fight her, together. A Kamen Rider and a Servant, it's a best match against her.

Mash nods as he picks something out of his pocket and he says something to Medusa.

Player: Hey, Medusa. Since you fight with a Rider that came from a Mirror World. I'll fight you alongside my friend with my own Mirror World Rider.

He shows her a new progrisekey he looted from his pocket. It's a red progrisekey with a Rider's face on the monitor and its motif on the SP symbol. He could feel the power flowing through it as he pressed the button.

MIRROR

AUTHORIZE

PROGRISE! 13 DRAGON KNIGHTS! FINALVENTING RYUKI!

One who can't survive without fighting.

(Play Ryuki Battle OST)

https://youtu.be/lkLpAfn9yi8

He transforms into another form, a red dragon medieval-knight theme with its dragon motif on top of its helmet, and also wields a dragon visor, the Dragvisor along with his card deck on the left side of his waist. He transforms fully into Kamen Rider Ryuki.

Olga and Mash were surprised that he too could transform into another Kamen Rider. But for Medusa, she became more psychotic knowing the battle would make it more interesting as she stands on the chains.

Medusa: Being too fresh can grate on the nerves.

She releases her hair which turns into snakes and then the same chains she's standing on. It blocked all of the exits as they were completely trapped by her chains. She picked up another card from her deck and inserted it into her Venovisor.

Advent

She summons back the Venosnaker as it hisses to Player and the girls with Medusa smiling thinking it's her victory. But for him, he silently pulls out his card as Medusa starts monologuing towards them. He silently inserts it into his visor, not activating it yet.

Medusa: I will entangle you all with my hair.

Player: Funny you asked, I think my dragon would entangle yours instead.

Advent

Suddenly the roar of a strange dragon was heard as he looked to the water. Suddenly his contract dragon, Dragreder, comes out from the reflection of the water breaking all of the chains, and starts attacking the Venosnaker. She was surprised by the fact her chains were easily broken apart by a dragon as she was immediately punched in the face and sent back to the ground.

The fight continues as he parries and evades all of her attacks and counters all of them as he gives her a beatdown. But then she disappears once more as she tries to deal a lethal blow to him but Mash switches places with him as she blocks it and this time she doesn't falter. Venosnaker fires its venom poison toward Dragreder but it learns its lesson as it dodges and starts biting to its neck. But suddenly they were all startled by a mysterious voice that echoed in their battlefield.

???: You got guts. A little girl is still a little girl, but you seem pretty strong. You on the other hand have a bold power that shook this place a little bit. That's why I can't leave you both like this.

Medusa: Who are you?

???: Who? Look at me and you'll know, old friend.

They look behind them to see the servant who sniped Emiya before. He knows who it is as he mutters his name. He removes his hoodie and shows his red eyes and slicked-back blue hair.

Medusa: You... Caster!

Player: Cu Chulainn...

Medusa: Why do side with these wanderers?

Cu: Huh, why? Because it's better than being on your side, of course!

Cu fires his attack towards her which causes her to back off from the attack. Olga takes cover behind Mash and her shield while he just covers his face with his arm. Cu walks up behind them as he explains the reason why he's siding with them for now.

Cu: I'm a Caster Servant. For a certain reason, I consider her an enemy. The enemy of my enemy is not necessarily my ally, but for now, you can trust me. Get in position, young lady. Skill aside, your courage is second to none.

Mash: Understood!

Cu: Young man. Are you the Master?

Player: I am, what's the game plan?

Cu: I'll leave it to you for the commands. It'd be a temporary contract, but out of regard for that brave young lady, I'll become your Servant. Also, looks like you know what is up with Lancer becoming like that.

Medusa: *smirks* That's fine with me. It means I can kill you earlier than planned. I'll take you all on while you're still flesh and blood.

Medusa started forming her broken chains into sharp spikes and launched them towards them. Player knows what to do.

Player: Cu, stall them!

Cu: I got it!

Cu then starts luring the projectiles as he dodges every single one of them and he starts engaging with Medusa.

Player: Mash, assist Caster. Both of us will flank her to force her to use "it".

Mash: Roger!

Mash then proceeds to get behind Cu's location and he inserts a card into his Dragvisor as he activates it.

Strike Vent

Cu dodges every attack she's swinging with her scythe-visor. He doesn't even have time to make a spell to attack her. Player fires his fireballs from his Dragclaw as he provides cover fire for Cu to set up his spell.

Medusa engages in a fight with him as he starts attacking her with his fireballs. She deflects it all as she is about to attack when all of a sudden she hits a hard material instead of him and she hears the voice of her belt.

Sword Vent

He now wields the Dragsaber as he starts pushing her back towards. Medusa looked at it and gets all cocky when she thinks she has the chance of finishing him off.

Medusa: All you can do is run away and let my prey fight me! You don't even have time to cast a spell, and this is what you get for opening your big mouth!

Cu: *smirks*

Medusa: !!!

Cu: Young lady!

Mash came at the right time as she blocked the attack and she was stunned for a bit. Medusa steps away from her and keeps her distance but she doesn't know what is coming next as Cu starts to talk to her about his Runes' casting.

Cu: I don't need to chant a spell to use Runes. Maybe you're the one who has a big mouth. So go back to witch school, you dimwit!

Medusa looked down to see a rune set up and activated a flaming rune trap. She screamed in pain as it exploded beneath her. She was now getting exhausted but she was not going down without a fight.

Medusa: GRAAAAAAAAAAGH!!!!!!

Medusa suddenly unleashes a powerful purple aura that causes the Venosnaker to push back Dragreder and get behind her. Dragreder knows what's up and follows up by getting behind Player.

Medusa: All of you, my prey!! You're blood, your flesh!! Mine, MINE!!

She then pulls out a card of her deck's motif and inserts it into her Venovisor. The player then picks up his original Progrisekey and scans it to the driver while Mash and Cu get on guard as they know that whatever she's about to do is spelling dangerous.

BITRISE

BYTERISE

KILORISE

MEGARISE

GIGARISE

TERARISE

After that, he pushes the Progrise Key in his Driver and Medusa activates her own by inserting it into her Visor.

Final Vent (Veno Crash)

FINALVENTING TERA-IMPACT (Dragon Rider Kick)

She runs towards Mash and Cu with Venosnaker slithering behind her before jumping into the air. Venosnaker spits a stream of venom at Medusa, propelling her into a flying bicycle kick that strikes both Servants.

He thrusts his arms as he is tensing his muscles and he jumps into the air with Dragreder flying behind him. The Dragreder then breathes fire at Ryuki, propelling him into a flying kick that targets Medusa.

https://youtu.be/hVdFGTaB37k

Mash is the only one taking the blow with her shield and cannot hold on for much longer. Player strikes at Medusa with his finisher as she stomps to the ground and a massive explosion erupts from the finishers.

(End OST)

As the smoke clears, Medusa is only standing there with her contract monster screeching and hissing as it fades away from the real world. Her contract card deck has been shattered and she's fading away by turning into purple light particles. She just stood there and couldn't believe it, considering herself the most powerful servant in this place has been easily defeated by a similar power to hers.

Medusa: How can I lose... to a Rider like you?

He just disengages his transformation and turns back into a human. She was shocked to see it was all just a human who defeated her in the end. That's all she could say before fading away completely admitting her defeat. Olga and the rest can only watch the spectacle, knowing the battle is finally over.

Cu: That's another one down and out.

Mash: Thank you. You saved us when we were in danger.

Cu: Well, good work.

Cu just head pats her as he gets near to his temporary Master and he talks to Mash about something.

Cu: You have a fine body like him. When is your wedding?

Player immediately blushed from this including Mash and Fou was just hissing at Cu. Cu finds it funny and just laughs at it while Olga is just sweatdropped from this.

Olga: That's one sexual-harassing old pervert.

Romani: For now, let's ask him about the situation. It seems he's a sane Heroic Spirit from this place.

Cu suddenly saw the hologram of Romani and was curious about the technology behind it.

Cu: Oh? Is that some means of communication through Magecraft?

Romani: It's a pleasure to meet you. Heroic Spirit, I don't know where you hail from, but it's an honor-

Cu: *sigh* There's no need to be so formal. Just state your business quickly. You're good at that, right, weakling man?

Romani finds that somehow offensive as he just points to himself with his eyebrows twitching.

Romani: W-Weakling...?

Player: You'll get used to it, Dr, Roman. Come on, let's go find someplace where no one can eavesdrop on us talking about what the heck is going on.

They all left the vicinity as their problem is still lingering and the context must be told. The Kamen Rider's journey continues with more and more questions than answers.