Y/N, Sonic, Tails, Bunnie, Tommy, Rotor, and Fiona took the Tornado and Twister to explore around the abandoned facility that was a source of some weird seismic activity. Y/N had to leave Kirby in her treehouse that no one else still haven't figured out where she had gone to keep him safe and that it was dangerous. She promised him a good sweet treat when she gets back much to his joy. While Sonic was exploring one part of the facility without letting Y/N catch up, Y/N, Rotor, and Fiona were trying to catch up to him as Tails, Tommy, and Bunnie explore another part of the facility. When they caught up to him, they saw Sonic looked real hurt.

"Sonic!!" Y/N exclaimed, rushing over to him.

"Oh, my! He looks pretty bad!" Fiona gasped.

"Rotor to Bunnie! I need the medi-kit!"

"Copy that! I'll retrieve it from Freedom One and be back in a flash!"

Rotor leaned Sonic against the wall.

"Easy, Sonic! Just relax! I guess we stumbled onto something bigger than we could have imagined!"

"Are you alright, bro? What happened?"

"I'm okay! Just exhausted!"

"You look more banged-up than beat tired." Fiona commented.

"That obvious, huh? I ran into Shadow!"

Y/N's eyes narrowed.

"What...?"

"While you were playing around with the computers, I decided to check out the joint while waiting for the others to hook up with us. So we ducked it out for who know how long! Bottom line, that sucker can throw a punch!"

"Shadow may look like a hedgehog, but I don't believe for a second he's related to you in any way!" Rotor said. "In fact, I'm not sure he's even a Mobian like us!"

"That's because he's an ultimate life form." Y/N said, walking off.

"Sis? Where are you going?"

She turned to him with a glare.

"Isn't it obvious? I'm going to have some serious talk with him!"

Without a second, she rocket skated off before they could say anything.

"Is she out of her mind?" Fiona asked in worry.

"Don't worry about her. She can actually handle him. I hope she doesn't get too overboard..."

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Y/N skate through the hallway, searching where Shadow might be until she found him with a golden robot called Isaac.

"SHADOW!!!!"

He froze and turned to see her with a very angry expression.

"You and I are going to have a serious talk right here and now! I heard you beat up my brother!"

"WHO'S THAT? WHY DOES SHE LOOK SO ANGRY?" Isaac asked, pointing at her.

"That's Y/N... She's always angry when they did something bad..." Shadow slowly explained, feeling a little scared. "I don't have time to explain, Y/N."

"With what?!"

Before he could say anything, a stomp was heard and they turned. Y/N was in shock to see Metal Sonic that she thought she never get to see again.

"Metal Sonic?!"

"MY SENSORS REGISTER YOU AS ONE BIO-CYBERNETIC SENTIENT AND ONE APPROXIMATE E-100 AUTOMATION! IDENTIFY YOURSELVES OR BE SUBJECT TO DEACTIVATION!"

"A mechanical version of Sonic? Could my creator have built him as well?" Shadow questioned.

"MY CREATOR DESIGNS AND BUILDS ONLY CYBERNETIC CONSTRUCTS SUCH AS MYSELF AND THE E-100 STYLE MODELS!"

Metal Sonic pointed at him.

"YOUR LIFESIGNS REGISTER MUCH LIKE THE BIO-TRASH NATIVE TO THIS WORLD, AS WELL AS HAVING BINARY PULSES SIMILAR TO MINE. YOU DO NOT COMPUTE!"

"For a mechanoid, you register distinctly hostile tone!"

"Isn't that obvious?" Y/N rolled her eyes.

"AND YOU SHOULD HOLD YOUR TONGUE WHEN SPEAKING TO YOUR SUPERIOR!"

"Superior?"

A stretched fist punched Shadow in the face, causing him to fly back and fell to the ground. Metal Sonic brought his fist back, walking towards him.

"Shadow!" Y/N exclaimed.

"I AM NOT THE LESSER BEING NOW LICKING HIS WOUNDS!"

"What wounds? In case you hadn't noticed..."

Shadow stands up and punched him back, sending him flying.

"...I'm not the one now having trouble staying on my feet!"

Metal Sonic shook his head and goes to attack Shadow when Y/N jumped in and kicked him straight in the face.

"Remember me?"

She glared at him, bringing out her katana. Metal Sonic glared back.

"NOT THAT I KNOW YOU. BUT YOU ARE A SISTER OF SONIC THE HEDGEHOG. AND YOU SHALL BE FINISHED!"

He goes to claw her when she deflect them with her katana as the blades clashed against each other, creating fire sparks. Shadow comes over to Y/N's aid and grabbed Metal Sonic by the legs and threw him against the wall as the falling debris hit him. Metal Sonic brought out his feet and fire out lasers towards them. Shadow quickly made her go behind him as the blast hit him straight in the chest, sending them flying. They both fell to the ground as Shadow wasn't affected from the blast much to her relief. Her eyes widen to see Metal Sonic goes to pounce them and quickly saw a broken piece from the floor and grabbed it out and threw it straight into the robot's face.

"That rocks, guys! What do you do for the encore?" Sonic grinned, leaning agains the wall.

"Sonic!" Y/N smiled.

"A NON-HUMAN SPECIES CAPABLE OF INTELLIGENT SPEECH? INTRUIGING." Isaac said.

"I've encountered Sonic before! He and his friends as well as Y/N are all like that!" Shadow said, helping her up.

"THIS WARRANTS INVESTIGATION. PERHAPS EVEN NECESSITATING DISSECTION."

"Dissection?" Y/N questioned.

"Is that anywhere near Village Center and Pine?" Sonic asked.

"IT DISPLAYS WIT, IMPLYING INTELLIGENT THOUGHT, THEREFORE IT COULD BE DANGEROUS--"

"Me? Dangerous?" Sonic pointed at himself.

"--AND MUST BE DEALT WITH."

Issac fired blaster at Sonic who quickly jumped, dodging it.

"Hey!!!"

Shadow threw a punch at Sonic, but he dodged that too.

"I agree!"

"Two against one? You guys don't stand against a chance!"

"THEN HOW ABOUT WE MAKE IT THREE?" Metal Sonic asked.

"Seriously?! You're all fighting Sonic?!" Y/N exclaimed in shock at what she was seeing.

"Can't help cutting into the act, huh?"

Y/N decided that's enough as she joined her brother's side.

"How about two against all three of you?!"

"You got that right, sis!"

Him and Y/N curled up into a ball and spin dashed around the room, bouncing and hitting Shadow, Isaac, and Metal Sonic. They quickly ran or skated down the hallway with the three of them chasing on their tail.

"Say! That was funny! I was right about you mugs! No sense of humor!"

"This is no time to joke around, Sonic!"

"HOW ABOUT YOU QUIT RUNNING AND FIGHT BACK, HEDGEHOGS?"

"Who said we played by your rules? That's a sucker's game!

"IT WOULD APPEAR THAT I GET TO FINISH YOU OFF FIRST, SONIC."

"Delusions of grandeur, pal! That just ain't gonna happen!"

Y/N goes next to Shadow and elbowed him away, but he elbowed her back.

"No way am I letting you hurt him, Shadow."

"Nor will I ever want to hurt you."

Metal Sonic and Sonic began to wrestle as they ran.

"THIS IS IT, HEDGEHOG!"

"Not with your track record, it isn't!"

Suddenly, the floor opened up below them and all five of them fell into the darkness.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Y/N groaned, opening her eyes.

"You alright?"

She looked up and blushed to see Shadow as she realized she's in his arms in bridal style. She tried to get out of his arm, but his grip was firm.

"Y-Yes, I'm okay. Can you put me down now?"

"No, I like this." he smirked.

Her face turned red and all of the sudden, they heard rumbling. They turned and saw a train coming down the tracks really fast. Then, Shadow with Y/N in his arms, Isaac, and Metal Sonic jumped off the track. They turned and saw Sonic jump onto the train as it passed them. Y/N was about to shout to him when Shadow spoke first.

"Even if he's hurt, Sonic can run faster than that vehicle. So why use it?"

"A CHALLENGE, PERHAPS?" Metal Sonic guessed.

"THE PROBABILITY OF THAT OUTCOME IS 0.05%." Isaac said.

"What other reason, then?" Shadow asked.

"INSUFFICIENT DATA TO EXPLAIN THE MOTIVATION OF THAT PARTICULAR SENTIENT LIFE FORM. HOWEVER, HIS OPTIONS ARE CONSIDERABLY NARROWED ONCE HE REACHES THE END OF THE LINE. WE CAN FOLLOW IN OUR OWN CAR, ONE OF MANY THAT ARE PART OF THE NETWORK!"

"No, thank you, Isaac! I will get my answers through more direct means."

Shadow then took off with Y/N.

"You know I can move on my own, right?"

"Thought you could at least catch up to your brother."

They soon caught up with Sonic who's riding a train car and talking on his holographic watch with Isaac's voice in it.

"THE BOMB, WHICH WAS INTENDED TO PRESERVE THE PHYSICAL ENVIRONMENT AS IT WAS AT THE TIME. INSTEAD TRIGGERED VOLCANIC REACTIONS WHICH SENT BILLIONS OF TONS OF ASH AND DIRT INTO THE ATMOSPHERE! THIS IS WHAT IS KNOWN IN CURRENT ECHIDNA THEOLOGY AS THE FIRST DAY OF FURY!"

"Sonic! Y/N! Do you realize what he's saying?" Tails called through the watch.

Shadow and Y/N jump onto the train as he set her down on the back seat and suddenly grabbed Sonic from behind by the neck.

"Hey! Shadow!" she gasped.

"Can't talk, li'l buddy! I'm a bit all choked up right now! And thank goodness sis is here!"

Sonic then pressed the button on the cart and it stopped, sending Shadow flying forward.

"And I need a brake! Unhappy landings, you second-rate wanna-be!"

Y/N sighed. When will they learn to stop fighting at a time like this? Never...

"IN ADDICTION, BESIDES TRIGGERING THE DEVOLUTION OF HOMO SAPIENS, THE BOMB ACCELERATED THE EVOLUTION OF WHAT WAS ONCE REFERRED TO AS THE ANIMAL KINGDOM." Isaac continued to explain. "THIS PROCESS LASTED FOR WELL OVER A THOUSAND YEARS UNTIL THE SUN FINALLY BURNED THROUGH THE LAST OF THE ASH AND DIRT IN THE ATMOSPHERE. IT WAS AT THIS JUNCTURE, DURING ONE OF HIS INFREQUENT FORAYS FROM THE LIFE CELL CHAMBER, THAT KINTOBOR ADDED HISTORICAL EVENTS TO THE LIST OF SCIENTIFIC DATA I WAS TO COLLECT."

Sonic and Y/N got off the cart and tiptoed down the hallway. They turned down the volume on their watch as she has one too. They head into the dark room and the door closes behind them. A few seconds later, Shadow forced the door open with his own hands. Y/N was surprised at how strong he is. He isn't called the Ultimate Life form for nothing.

"Give it up, Sonic! Show yourself so we can talk!"

Sonic just spin dashed him the face. He held his foot in pain.

"What are you made of? A brick wall? I don't get any of this! Why all the hassle in the first place?"

Sonic ran for the nearest door with Y/N right behind him.

"SOME SECRETS WERE NEVER MEANT TO BE DISCOVERED. UNFORTUNATELY FOR YOU, HEDGEHOG, YOU'VE STUMBLED ONTO THE MOST FATAL SECRET OF ALL."

Isaac was right as they found a giant rocket with the word "Titan GX". Y/N gasped, knowing that this is trouble. A big trouble.

"Secrets? What secrets? And who would I tell?" Sonic asked in confusion.

"What is all of this?" Y/N asked, pointing at the giant rocket.

"WHILE THERE'S A 93% POSSIBILITY YOU COULD BE STATING THE TRUTH IN YOUR LACK OF COMPREHENSION WITH REGARD TO THE SITUATION YOU NOW FIND YOURSELF IN. THERE'S A 74% PROBABILITY YOU UNDERSTAND THE SITUATION BEFORE YOU AND ARE PLAYING FOR TIME." Isaac said.

"Hey, if you think I could pull one over you or you Metal, or even you, Shadow—"

Isaac shot a blast at the hedgehog siblings, but they dodged it by jumping over.

"—then I guess we'll have to try harder next time—"

They bounced off of Isaac's head.

"—cause what fun is it if you already know?"

Y/N and Sonic started running or skating up the walls. Metal Sonic fly after them in the air.

"SURRENDER TO ME, HEDGEHOG AND I'LL SEE TO IT THAT DR. ROBOTNIK WILL BE QUITE MERCIFUL TO YOU! AND THEN YOUR SISTER!"

"Ha! Good one! I see he's programmed you with some comedy routines...!"

"Again! This is no time to joke around!"

"WHY GO THROUGH ALL THIS EFFORT? YOU'LL BE EXHAUSTED BY THE TIME YOU TWO GET TO THE TOP, IF YOU AREN'T ALREADY UNABLE TO PUT UP MUCH OF A FIGHT WITH THE END RESULT THE SAME!"

"About that suggestion of yours—"

Sonic and Y/N slammed Metal Sonic on the side of the rocket.

"—here's our reply!"

"IS THIS YOUR WAY OF SAYING NEGATIVE?"

"Yeah! You might put it that way!"

Y/N is getting tired with all of this. Metal Sonic, Isaac, and Shadow chasing and gaining on her brother when he just want a simple break. And then, there's her with Shadow not wanting to hurt her, Isaac sometimes tried to shoot her, but mostly on Sonic. Not sure why. And then there's Metal Sonic who clearly sees her as a target too once he deals with Sonic. She turned to see Shadow coming straight towards Sonic when he spin dashed away and Metal Sonic crashed into Shadow and they fell to the floor.

"Ouch..." Y/N winced at the scene.

"Oooh, that's gotta hurt!" Sonic grinned.

He was about to jump away when Shadow appear out of nowhere and grabbed his ankle.

"Forget something?"

"When did you get here so fast?!" Y/N exclaimed in shock.

"Yeah, like the reason you're so hostile! What'd I ever do to you?" Sonic asked.

Shadow threw a punch at him, but he dodged it.

"A fair question! I sense you are an enemy, but I know not why!"

Y/N quickly put Shadow in a headlock.

"Then, stop trying to hurt him!"

"Yeah! Sounds more like a lapse to the synapse in that noggin of yours. Maybe if you tried meditation or maybe found yourself a girl, you might get a handle on all your pent-up aggression!"

Shadow softened a bit to hear a word 'girl' as it clearly goes to Y/N. He quickly shook his head and glared at Sonic. Shadow then kicked him in the stomach.

"Oof!"

Shadow grabbed Y/N from behind him and flipped her over his shoulder. Y/N quickly landed on her feet.

"Maybe I just don't like your attitude!"

"Aww, what's not to like?"

"Your cockiness." Y/N deadpanned, causing Shadow to snicker a little.

"Hey!!"

All of the sudden, the room started filling with stream.

"Say, does the steam seem to be getting thicker to you?"

"I will not be distracted by such a childish ploy!"

"Shadow! He's not kidding! Can't you see the steam?" Y/N said.

"Me kid you? Where's the percentage? By the way, seen your friend Isaac around?"

Sonic pointed his thumb at Metal Sonic in the small crater.

"I see Ol' Sparky over there, but it looks like Mr. Personality cut and ran!"

"You're right! Where do you suppose to?"

Y/N pointed at the rocket.

"Anywhere there wasn't one of these about to go off at any minute! The way out is blocked!"

"Guess it's every robot for himself!" Sonic commented.

"Shadow's not a robot, you idiot!"

"Then what is he?"

"I— am not sure."

Y/N patted his shoulder.

"You're Shadow. You just don't know it yet. But I know you'll figure this out on your own."

Shadow gave her a small smile.

"How about we debate that question later? Suppose we race upstairs and see if there's a better way out!"

The three of them raced off. A few minutes later, they made it to the upper floor. Y/N noticed Sonic started to get tired.

"Boy," he panted. "that really does take a lot out of you! But you— you guys didn't even break a sweat!"

"That's because I'm in my roller skates. It's easy for me to move faster." Y/N stated.

"I knew that."

Sonic found a doorway.

"Hold it! This baby is set to launch, right?"

"Yeah?"

"I guess!" Shadow said.

"Then we have one last chore before splitting!"

"Let's go then!" Y/N shouted.

They quickly made it outside through the hole of the ceiling. Down below them, Tails, Bunnie, Rotor, Tommy, and Fiona were getting on board the Sky Patrol. Uncle Chuck was down there too.

"We're out!" Shadow said.

"It's like a war zone out there!" Sonic said.

"And there's our friends!" Y/N smiled in relief to see them again.

"But I'm not gonna make it! My ankle's shot!"

"What?" Y/N asked in worry. "Why didn't you tell me?"

"I didn't want to worry you, sis."

"Just shut up and get into your spin mode!" Shadow said, grabbing Sonic and throw him towards the Sky Patrol.

"Hey! Wait!"

"What about you, Shadow? Come with us." Y/N said, turning to him.

Shadow said nothing and pulled her into the kiss. She was shocked before he pulled away.

"I create my own path to follow."

"O-Okay. Be careful out there."

Y/N nodded, blushing and zoomed off as they went their separate ways. She made it on time in front of the Sky Patrol to see Sonic landed on his butt painfully, catching Uncle Chuck's attention as Rotor got onboard.

"Sonic! Y/N!"

"Uncle!"

"There couldn't have been an easier way could there?" Sonic asked.

"Nope!" Y/N said.

They soon aboard the Sky Patrol. Y/N turned to see her dad piloting.

"Don't spare the fuel cells, Jules!" Uncle Chuck scolded him.

They then took off as the whole building exploded behind them.

"We never did learn what caused the seismic graph to go off the charts!" Rotor said.

"There's a lot more we didn't figure out!" Sonic sighed, leaning back against the seat. "What exactly was that place? Who built it? And why?"

"You never read this book, Sonic?" Tails asked, showing him the book.

"That guy?! He's a crackpot! He wrote all these wild claims about what life was like on Mobius thousands of years ago."

"And he may yet be proven right! If only we could have brought Isaac back for study, 'cause I'll bet your spines would curl at what he could tell us!" Rotor said.

"He's got the point. While Shadow and I were catching up to you, I've overheard the history from Isaac himself and there's a lot going on that we never get to learn." Y/N said.

"Shadow? Who's this, Shadow?" Jules asked, looking over his daughter.

"He's just a friend, dad. Don't worry."

"Did he do anything to you?"

"Yeah, sis, did he do something after he threw me off?" Sonic asked, raising his eyebrow.

Y/N recalled Shadow kissing her before taking off.

"No, no he didn't."

"You're lying. Your face showed, Y/N. Tell me..." Jules narrowed his eyes, seeing her face turn pink.

"I told you! It's nothing!"

"You're lying again, daughter."

"I'm not!!"

"Sis, is it true? He did do something didn't he?" Sonic asked, leaning over her with a suspicious glare.

"No! He didn't! Stop pestering me, you two!!"

"Boys, leave her be." Uncle Chuck said. "And focus on your flight, Jules."

"Thank you, uncle..." Y/N sighed in relief.