"Rengoku!" Lynn yelled with worry before covering herself when a small shockwave blew through the area as Rengoku and Akaza continued to clash against one another. 

Thunderous sounds of fleshing being cut and banged against metal filled the air as you, Lynn, Tanjirou, and Inosuke watched Rengoku fight against Upper Moon Three, Akaza. The Flame Hashira dodged three strikes from Akaza and tried to counterattack with one good slash, but the Upper Demon dodged with ease as Rengoku was forced to block five furious attacks with his blade. Akaza followed up with two more punches before sending a spinning kick that moved Rengoku back about a foot before he parried one punch and brought his blade down to catch Akaza's left hand by the wrist, digging his blade deep into his arm. 

"Please, my Lord!" Lynn begged, but you remained silent and continued to watch from the sidelines. "He really isn't going to help him...?" She couldn't believe what you were doing while turning her head back towards the fight.

Rengoku barely had enough time to react to Akaza's deadly chop and sliced upwards to amputate his right arm, but it would be a futile effort as Akaza grinned as his limb grew back in an instant and he used the same arm to force Rengoku to block. Reeling back his left arm with glee, Akaza sent another power blow that Rengoku clashed with as sparks and blood flew in the air between the two of them. The two of them were face to face before Rengoku let out a powerful yell while slashing towards Akaza, making the demon leap back high into the air before he suddenly spun around and entered a strange stance.

"Destructive Death..." Akaza's hands briefly had a strange aura around them before he closed them into fists and reeled back his right arm. "...Air Type!" He threw his fist forward with great force as Rengoku waited to see what attack was coming towards him.

Rengoku scanned his surroundings before coming to a realization of the kind of attack he unleashed and feeling a strange force come towards him, the Flame Hashira raised his sword in time to block an air punch that almost knocked the wind out of him. Akaza flipped over right-side up and sent two more air punches as Rengoku blocked those as well, sliding back a few feet before regaining his footing.

"I see..." Rengoku thought as he watched Akaza unleashed six air attacks. "Flame Breathing...Fourth Form..." He adjusted the grip on his blade before moving it in a circular motion with great force. "Blooming Flame Undulation!" He unleashed his fourth technique that absorbed the all of the air attacks thrown at him. "When he strikes the air with his fist, the attack will reach me here!" He thought as Akaza unleashed another volley at him and Rengoku performed the same technique to counter before Akaza landed back on the ground a few feet away from him. "He can move faster than the blink of an eye. If I allow him to fight from a distance like this, slicing his head off will be tricky. In that case..." Rengoku assumed a strong stance before he moved faster than Tanjirou and Lynn could see.

"Hmph, good battle sense." You said as you saw Rengoku close the distance between himself and Akaza. "Realizing his best chances are to remain up close, he'll use his speed to make sure Akaza won't be able to use his ranged attacks. I guess you shouldn't expect any less from a human of today who's bloodline has been slaying demons for quite some time. However, they're still on even ground." You watched as Akaza smiled before clashing with Kyojuro once more in a violent volley of attacks that the two were letting off, creating thunderous shocks through the area they were in.

Watching the two of them trade blow after blow in such an intense manner, Tanjirou tried to get back on his feet to try and join the fight. Before he could however, Rengoku took notice mid-fight and glanced back to Tanjirou.

"Stay where you are!" Rengoku yelled as Tanjirou and Lynn stopped moving, along with Inosuke who had just gotten back to the scene. "If that wound reopens, it'll be fatal! Stand back! That's an order!" He yelled at Tanjirou before putting his focus on the battle.

"Don't bother with those weaklinigs, Kyojuro!" Akaza said while blocking his blade with his arm before swiping it away. "Come on, give me your best shot!" He yelled with excitement while trying to spear poke Rengoku, but the Flame Hashira sent a slash towards his abdomen, forcing to jump back as he stared at him with a grin. "Concentrate on me." He said as he was having fun with the whole situation while watching Rengoku charge towards him. 

You watched Rengoku clash once more with Akaza before using his strength to send the Upper Moon demon flying into the forest where a huge dust cloud erupted from the force Akaza was flung with. The Flame Hashira ran into the woods in search of his prey but didn't need to look far as Akaza had leaped in front of him with a wide grin, praising Rengoku for his skills as they traded blows once more, Rengoku being able cut off one of Akaza's arms before the demon kicked him away, sending him back to the railroad as Rengoku crashed against the mound of the train tracks.

"Rengoku!" Tanjirou yelled in worry.

"Ol' Goggle-eyes!" Inosuke was shocked.

"Are you okay?!" Lynn was beyond concerned as Rengoku sat up while keeping his sights on Akaza as he walked out of the forest.

"Turn into a demon, Kyojuro." Akaza said while walking out of the smoke as Rengoku leaned against his sword and tried to catch his breath. "Fight me forever and get stronger together with me. You have what it takes to do that!" He said while regenerating his arm. 

"I'll pass!" Rengoku reaffirmed his decision as gripped the hilt of his blade and used it to push himself back to his feet. "Let me repeat it. I don't like you!" He said while raising his blade once more and pointing it towards Akaza. "I will never become a demon!" He yelled while leaping towards Akaza with his blade raised above his head. "Flame Breathing, Third Form! Blazing Universe!" Rengoku unleashed a powerful slash that managed to graze Akaza when he tried to evade his attack.

"Magnificent! That's sensational!" Akaza was beyond ecstatic over Rengoku's strength as he dashed back towards Rengoku, making him jump back. "Destructive Death! Air Type!" He sent another air punch towards Rengoku, making him block as the force was enough to push him back a few feet.

The two of them charged towards one another once more as their battle was beginning to reach its climax. You watched and began to get impatient of wondering when Akaza would finally kill Rengoku, as you knew that the Flame Hashira was no match for the Upper Moon demon. Lynn and the others watched in fear as Rengoku sustained a cut above his left eye that was later smashed by Akaza's fist. Slowly the gap between Rengoku and Akaza became more apparent as the Hashira was struck in his abdomen, crushing a few of his ribs before he forced Akaza to jump away from a slash. After the two split, the only thing audible from the battle was the heavy breaths that Rengoku was trying to gasp for as his subordinates could only watch on edge and in fear while Akaza was perfectly fine. 

"This battle is already over." You commented while closing your eyes as despair began to fill Lynn and her friends hearts as Akaza was beginning to get frustrated by Rengoku's resistance.

"Even if you fight to death, you can't win, Kyojuro. Those impressive slashed you inflicted on me have already healed completely." Akaza said while a cut across his chest healed at his own will. "But what about you? A smashed left eye, shattered ribs and damaged internal organs...All irreparable. If you were a demon, you'd heal in a blink of an eye. Those would be mere scratches for a demon. You can struggle all you want, but a human can never beat a demon." Akaza said as you opened your eyes and looked to your right to see Tanjirou try to stand up as he desperately wanted to help Rengoku.

"It's useless." You said as Tanjirou looked up at you in shock. "This is his last battle. You'd only die in vain alongside him." You said as Tanjirou was beginning to lose hope, but there was a sudden change in the air as you turned towards Rengoku. "This is..." You muttered as Tanjirou and the others looked closely to Rengoku.

The Flame Hashira exhaled briefly before the air around suddenly became hot and heavy as his fighting nature had risen to its highest. Akaza had sensed it as well as he was stunned by Rengoku's resolve. Sliding his right leg back into a power stance and raising his blade up behind his head, Rengoku gave his signature smile as he spoke out loud.

"I..." Rengoku spoke with all his will and resolve as he stared down Akaza. "I will fulfill my duty! I will not allow anyone here to die!" Rengoku proclaimed as he prepared himself for his final attack. "I'll damage his body as much as I can in an instant! Flame Breathing...Esoteric Art!" He assumed his power stance as his powerful aura sent shivers down everyone's spine except yours.

"Ahhh...! What a tremendous fighting spirit! Amazing aura despite all those injuries! That mental strength! That airtight stance!" Akaza smiled in absolute awe of Rengoku's true power as he chuckled in absolute entertainment and excitement. "You have to become a demon, after all, Kyojuro! Let's fight each other for all eternity!" He said to Rengoku as you noticed he was entirely focused on Rengoku now at this point.

"This is it." You thought while reaching down for your sword as Lynn noticed this.

"Is he going to help him now?" Lynn wondered before turning back to the battle. "Please, don't die, Rengoku...!" She prayed with all her heart as Rengoku steeled himself for this moment.

"Set your heart ablaze. Go beyond your limits!" Rengoku felt the fire in his heart spread out all across his body as he tightened his grip around his sword. "I'm the Flame Hashira...Kyojuro Rengoku! Ninth Form! RENGOKU!" He yelled the name of his final attack as Akaza prepared himself as well.

"Destructive Death...Annihilation Type!" Akaza chanted while lowering himself into a sturdy stance as the earth crushed under the movement of Rengoku's foot.

"HYYAAAA!!!!!!" Rengoku roared as he launched himself at unimaginable speeds for a human towards Akaza.

Rengoku moved with blazing speeds that made the air around him heat up as his attack was so powerful it roared like an untamed beast. Akaza giggled as he threw his hands in front of him and the opposing forces between the two created a massive explosion that blinded everyone with dust and sparks of fire created from the sudden heating of the air. The other slayers were beyond worried as they couldn't see what was going on. The sound of flesh being cut and mutilated was the only audible thing they could hear before there was a secondary explosion that broke the current of the air and began to dissipate the smoke. Lynn, Tanjirou, and Inosuke watched frozen in place as the smoke slowly began to clear. However, once two silhouettes could be made out, their worst fear had came true when the dust cleared to reveal Akaza had punched his right fist straight through Rengoku's solar plexus, sticking all the way out of the Flame Hashira's back as his arm was all the way in up to his forearm.

"Ren...goku...?!" Tanjirou could only mutter in shock and despair.

"This can't be...Rengoku, you're..." Lynn's hands began to tremble as Inosuke noticed a strange feeling coming from Lynn and he was shocked at what he saw when he turned towards her.

"Y-You...!" Inosuke couldn't find words to describe what was happening as the Tenseiga rattled wildly in Lynn's hands before she dropped it.

"You'll die! This will kill you, Kyojuro! Become a demon!" Akaza begged while his wounds all healed in an instant. "Say that you'll become a demon! You are...strong and one of the chosen ones!" He yelled before gasping when another presence appeared behind him.

"You lowered your guard, fool." Akaza gasped when you appeared behind him.

Blood spewed into the air as the three young slayers on the side all went wide-eyed when they saw you stab your blade through Akaza and also through Rengoku, trapping the demon between you two. You twisted the blade around as Akaza coughed up blood and slowly turned his head towards you.

"W-Who are....!?" Was all he could say before groaning in pain as you pushed your blade deeper through them.

"Tell me..." You said as you raised your left hand and placed your claws on Akaza's neck, emitting a green poisonous glow that burned Akaza. "...where is Muzan?" You said in an intimidating tone.

While captured between his own attack and yours, Akaza suddenly felt his entire body shiver as Muzan's cells reacted from the feeling of your aura. You picked up on this and leaned closer to Akaza's ears while speaking in a tone you knew your prey feared.

"I know you're listening, vermin..." You whispered as Akaza had a petrified look on his face as his body was losing control of itself. "...I'm coming for you." You said as Akaza began to cough blood, but you heard another breath as you glanced over to Rengoku. "He's still alive..." You thought as Rengoku resonated with the last line Akaza said to him.

"I am..." Rengoku thought faintly before his veins began to appear all over his body as he tightened his right hand's grip around his blade and yelled as he brought down his sword against Akaza's neck, making you lean back to avoid the blade that almost struck your face. "Mother...It was an honor for me to have been born to such a person as you!" Rengoku thought as he remembered the last things his mother said to him before her death, how he who was strong, had a duty to protect the weak, and how she entrusted everything to him. "AAAAHHHHHHHH!!!!!!" Rengoku yelled as his blade cut deep into his neck.

"Slayer, do not interfere. I'm about to get him to--!" You stopped midsentence when you heard a scream come from your left.

"Rengoku!!" You turned to see Lynn running towards you three with blood red eyes and a white streak running through her hair as claws emerged from her finger nails and her teeth became sharp like fangs. "RRRAAAAAAAHHHHH!!!!!" Lynn leaped at Akaza as you pulled your blade out and jumped away. "DIE!!!!" Lynn screamed as she grabbed onto Rengoku's blade and began to pull in the direction Rengoku was cutting in.

"Lynn!" Tanjirou yelled with worry as you furrowed your brows from the sight of her appearance.

"This presence, this scent...was this an effect of leaving the Tenseiga in the hands of a human?" You thought as there was no other explanation for what you were seeing as Lynn screamed while trying to rip the sword through Akaza's neck. "...She's turned into a half-demon." You watched as Lynn growled and began to claw at Akaza's face.

"GET OFF!!!" Akaza yelled in fury as he used his free hand to keep the blade in place and moved around to try and throw Lynn off, but he struggled greatly. "What the hell!? What happened to this brat!? She was one foot in the grave a moment ago, but now she has strength that could match an Upper Moon rank!? Impossible!" Akaza thought as he groaned in pain tried headbutting Lynn while she continued to claw at his face and pull Rengoku's sword through.

"HOLD ON TIGHT!! WE'RE ALMOST THROUGH!" Rengoku screamed as he used his free hand to try and push his sword through Akaza as well and you noticed a glint of light shine on your sword as you turned to see the sun rising.

"It's almost morning." You thought as you turned back towards Akaza. "I need him alive." You said as you began to walk towards him.

"The sun's coming up! There'll be sunlight here!" Akaza thought in fear as he was able to see the sun rise coming over the horizon. "I have to get out of here! I have to get away!" Akaza thought desperately as he tried harder to pull the sword out of his neck. "RRRAAAAHHHHHHHHH!!!!!!!" He let out a bellowing scream that pierced everyone's ears and made them struggle, except for you.

"No way are we ever letting go! NOT UNTIL WE CHOP YYOUR HEAD OFF!!" Rengoku yelled as he poured his last strength into pushing his sword through Akaza's neck. "AHHHHHHHHH!!!!!!" The three of them yelled as they continued their struggle.

"OUT OF MY WAY!!!" Akaza screamed in fury.

"HHHRRAAAAAAHHHHHHHH!!!!!" Rengoku roared with all his might.

"JUST DIE ALREADY!!!!!" Lynn growled as she began to cut herself against Rengoku's blade from pulling so hard, but they were now more than halfway through Akaza's neck.

"Move, Inosuke!" The boar headed slayer turned to see Tanjirou running towards the battle after retrieving his blade. "MOVE YOUR BODY FOR RENGOKU'S SAKE!" Tanjirou pleaded as Inosuke ran ahead and leaped into the air.

"Beast Breathing, Fang One! Pierce!" Inosuke pointed his blades towards Akaza's eyes.

"Enough!" You appeared between everyone and brought down your claw on the base of Rengoku's sword, shattering the blade and letting Akaza break free.

Akaza used all his strength and ripped his arm off from inside Rengoku as he leaped in the air with Rengoku's blade in his neck still and the force he generated was enough to blow everyone except you away as Tanjirou and Lynn watched in shock when they saw Akaza had escaped death. Akaza flipped backward and landed on his feet before taking a look to see how close the sunlight was beginning to get to him.

"I have to find refuge from the sunlight!" Akaza thought while regenerating his wounds and leaping into the darkness of the forest.

You had grabbed Lynn and held her down by your foot as she thrashed around like a wild animal and you put your sword away and watched as Tanjirou ran over to the spot Akaza fled from and he raised his blade up before throwing it into the forest. With your enhanced hearing, you were able to hear that Tanjirou's blade in fact made contact with Akaza, but it was meaningless as his footsteps grew further away.

"Don't run away! Don't run away, you coward! Don't run away!" Tanjirou screamed at the top of his lungs in anger as you all listened closely to what he had to say. "The Demon Slayer Corps...is always fighting you demons in the dark of the night where you have the advantage! That's right, us flesh and blood humans! Our wounds don't close up that easily! And we cannot regenerate a limb once lost!" Tanjirou vented as he shut his eyes in frustration. "Don't run away, you bastard! You bastard! You coward! Rengoku is way more amazing than you! He's stronger! Rengoku didn't lose! He didn't let anyone die! He fought to the end! He protected them to the end! You're the one who lost! It's Rengoku who won!" Tanjirou screamed at the top of his lungs with tears pouring down his face before he broke down and began to cry.

"Tan...jirou...!" You looked down to see that Lynn's eyes had returned to normal before she passed out, but her canine fangs and claws didn't disappear and neither did the white streak in her hair.

"The transformation must worn her out completely. She'll be out cold for a while." You thought as you took your foot off of her and turned around. "Now then..." You walked in the direction of Rengoku as he grew a confused look of why you were heading towards him, but was more surprised of how you just ignored him.

"Where will...you go now...?" Rengoku asked as you stopped and stood over the Tenseiga before picking it up and placing it at your side.

"If it has any meaning to you, I'm going after that vermin. He will lead me to Muzan." You said as you began to walk towards the tree line, but were stopped when Tanjirou stepped in front of you with a furious look. "Out of my way." You told the boy.

"Why didn't you help us...? Why would you do such a thing to Rengoku...!? How could you?!" Tanjirou screamed before he was met with a backfist as you sent him flying to the side as he landed next to Lynn. 

"I have no desire to listen to your pathetic pleas or frustrated ventilations." You said as Tanjirou could barely push himself off the ground as he stared at you. "The fault lies with you all just simply not being strong enough, and for getting in my way. I'm not here to help you with your dreams, I'm here to just squash Kibutsuji Muzan under my heels once and for all. I have no time for useless qualms like the death of your dear Flame Hashira." You said while walking into the forest. "He will die, and there's nothing you can do about it, and I have no desire in helping him." Your words cut deep as Tanjirou and the others were left despaired over Rengoku's situation, and their hopes of all of them surviving the battle, were shattered by your desires to kill Muzan.