‘Why is it? The thought of gaining power through this trip doesn’t make me feel good? It’s almost as if…this trip….one that I was starting to like…it has been corrupted.’

Ai slowly walked beside the train, towards where others were, thinking about why she wasn’t as happy. She shook her head, slapping her cheeks, “No matter! This isn’t about that power for me! I am here to have fun, meet people, and do things my way!”

*BOOM*

“Hm?” Ai raised her head, seeing a flash fall in front of them with a blast, “Another one?”

She started running forward toward where the blast was. Even though it was only for a moment, she felt a sense of dread spreading through her body; someone compelling had landed here. In the worst-case scenario, Muzan, Upper Six is the best-case scenario from Upper One to Upper Six.

When she reached them, Tanjiro was lying on the ground, injured, and the Demon with Upper-Rank Three in his eyes was asking Rengoku, “Why don’t you become a Demon?”

“Hmm? No thanks,” Rengoku exchanged a look with Ai, gesturing her to protect Tanjiro without words.

“Oh, another one is here; so many of these weaklings are getting between us,” Akaza, who had already introduced himself to Rengoku, smiled, “I can tell that, unlike any of them, you have developed your fighting spirit to the Edge of Perfection.”

“I am the Flame Hashira, Kyojuro Rengoku.”

“I am Akaza; let me tell you, Kyojuro, why your power will never truly reach perfection. It’s because…you are human. Because you will eventually age, and eventually, you’ll die.”

“Become a Demon, Kyojuro. If you do, you can train for hundred of years and keep getting stronger.”

“Growing old and dying…is what gives meaning and beauty to the brief span of human life. It’s precise because we age and die…that our lives have value and nobility. Strength is not a word…that means much regarding flash. These two aren’t weak…do not insult them,” Rengoku’s face became solemn, “You and I value different things. I have many reasons for not becoming a Demon.”

Ai had been breathing slowly, maintaining the constant Wood Breathing. She knew it was coming closer, the moment she had been waiting, the moment the two fought, the moment that Akaza didn’t have the luxury to stop her.

“Technique Development! Destructive Death: Compass Needle!”

Akaza jumped towards Rengoku, who used the first form and pushed forward.

“Now! Wood Breathing! Third Form! Breath of Life!”

She slashed towards Tanjiro, and the sword’s tip touched his chest; wooden roots came out of the ground, wrapping themselves around his body lightly.

“This is?” Tanjiro looked toward the branches and left in surprise. He could tell because Rengoku taught him to look inside and control his internals and muscles to a point to stop the bleed. He could tell that all this warm energy that was being poured inside of him that filled him was healing his wound at a rapid pace. It wasn’t the same level as the High-Level Demon’s healing, but it was good enough to heal him rapidly.

It didn’t just heal him, but Zenitsu, Inosuke, and everyone in and out of the fallen train.

“Hohoho! Is it possible that I underestimated you?!” Akaza jumped in the sky, looking toward them.

“Good job, Ai! Protect them and leave this to me!” Even before Akaza thought of attacking them, Rengoku blocked his path.

“Thank you, this is an amazing technique,” Tanjiro sat up, looking for his sword.

“Don’t be,” Ai had a grave expression on her face, “I shaved months of your life by healing you using this technique. I accelerated Cell Division and increased your regeneration powers.”

“It’s better than lying down and dying,” Tanjiro wasn’t phased for a moment. He ran towards his sword, picked it up, running back to Ai, who had a smile on her lips as she watched the two flash, fighting against each other.

“You have a point,” Even though Ai said she felt sweat collecting on her cheeks.

‘I underestimated them,’ Ai bit her lip until it bled, narrowing her eyes.

She easily defeated Lower Level Five, and One wasn’t much challenge, a bit time-consuming, so she thought it would be alright, maybe she could take an Upper Rank.

What boasted her confidence was that she captured Shinobu, even if she caught her off guard. Now she knew the difference was still huge; there was no opening for her.

Even if she wanted to heal Rengoku, she needed him to stay in one place and someone to keep Akaza busy, but there was no one here who could defend against him or stay alive for more than a few seconds.

“Rengoku…” Ai could see he was severely injured, and there was no way to help him.

“I will fulfill my duty! I won’t let anyone here die!” Rengoku’s perpetually happy smile appeared on his lips as he raised his katana.

“Haha, such fighting spirit! Even with those wounds…you are full of determination and spiritual fortitude! Your stance has no weakness! You should become a Demon, Kyojuro! Then you could fight with me forever!”

Akaza lowered his stance, “Technique Development!”

“Flame Breathing: Esoteric Arts!”

“Destructive Death!” “Ninth Form: Rengoku!”

Ai’s eyes widened to the extreme; in that one moment, before the collision took place, she could see it. She could see the future; she instinctively knew, ‘He’s going to die.’

That one thought overwhelmed her to the point she felt something break in her head, and the thoughts disappeared from her mind, “Wood Breathing: Tenth Form! Deep Forest Emergence!”

Both Akaza and Rengoku felt it, the ground beneath them trembled, and dense growth of trees broke the land apart, rising all around them, moving towards Akaza, forcing him to back away, “A forest out of nowhere?!”

“Wood Breathing: Third Form! Breath of Life.”

Rengoku felt a sword pass through his body, even though Ai was nowhere near him. His body started healing rapidly, confusing half a year’s worth of life force.

He was distracted; for one moment, he was, and Akaza went on the offensive, breaking the trees, closing the distance between him and his target.

Rengoku followed him with his sight, his hands raised since he was watching them in unbelief at the last moment, the fact that they healed so fast.

Now, his gaze was followed by Akaza, closing the distance between him and Ai, and at the moment before he made contact, Ai pushed Tanjiro away, saving him from Akaza’s strike, but the Demon managed to take away a chunk of flesh from her waist.

“AIIIIIII!!!!!!!!!!!!!!!” Rengoku raised his katana above him; Flames raised from his right and left, the right one moved clockwise, and the left one moved anti-clockwise, meeting in between, above his head.

‘Ah…so that was it….’ Ai felt her body fall forward, and the time slowed down. What came to her mind wasn’t her death but a memory from about a month ago.

Demon Corps, Training Grounds, One Month Ago,

“Alternate Flame Breathing! Seventh Form! Great Fire Annihilation!” Ai made a crescent slash, creating a sea of fire that covered the training ground.

“Flame Breathing! Ninth Form! Rengoku!”

Rather than fighting the spread-out technique, Rengoku cut it apart from the middle, appearing in front of Ai, placing the blade on her neck with a grin on his lips, “My win.”

“Gee, what a surprise, I lost again,” Ai stepped back, rolling her eyes.

“Hahaha, no worries, you are getting better,” Rengoku patted her shoulder, “I have great hopes for you, Ai.”

Ai went to the side, taking a water bottle, drinking, “I know…I know. I am working on it.”

“Say, Ai, what made you decide to call the Breathing Technique as an Alternate? Rather than adding to the forms of Flame Breathing?”

“Because it doesn’t use the same pathways as the Current Flame Breathing. I made it so that I can get more options, stamina, and a portion of my body isn’t burdened for long when using the two Alternatively. Although there are few overlaps, changing too many times wouldn’t be good either.”

“Hahaha, I thought so! Good, call it Reverse Flame Breathing Technique from now on!”

“Why?”

“Because I say so!” Rengoku spoke with a straight face, causing Ai’s face to fall.

She scoffed, looking away, “Do you have to be so overbearing all the time? Oh well, I guess I can’t say no until I beat you. When I beat you, I will start calling it Alternate again!”

“You are a good fighter, but you will never defeat me,” Rengoku laughed even louder, with a mysterious glint in his eyes.

Present,

Rengoku glared at Akaza, even when Ai’s body fell to the ground. The fire from both sides was meeting at the sword’s tip; rage swelled in his eyes, “Grand Flame Breathing! First Form! Scorching Universe!!!!!”

He slashed down in an arc; intense heat spread out from him, intense heat that cut apart the trees, before the scorching fire burned them down, all of them moving towards Akaza, passing by Tanjiro, who was shocked from the turn of events when he fell, pushed away by Ai. 

“Amazing! Rengoku! You are the best after all!!!” Akaza couldn’t do it, the attack was too strong for him, too fast for him to escape, and his whole body was engulfed by flames, cut and burned apart simultaneously.

“Hah! Hah! Hah!” Rengoku gasped for breath when a sharp pain struck his stomach, shoulder, and thigh. He put his katana to the ground to prop himself up, dragging his legs as he walked towards Ai.

The flames from his attacks were still burning, crushingly so, having cut apart the land, burning the forest that Ai created, and the demon.

This was the strongest attack he could muster and the one that he was sure to have killed the Demon.

“Ai…” Rengoku fell on his knee, seeing a chuck on her waist missing, the blood that had overflowed. The injury had destroyed her internal organs too.

“Hey…” Ai was lying on her stomach, her right cheek touching the ground, her hazy green eye looking at him as a smile appeared on her lips, “That was...amazing…. thinking you took it even further…you know what…I always thought you were a monster in human skin.”

Rengoku closed his eyes, his lips trembling, “I am sorry…it was my weakness…it was my fault…I should have been stronger….”

Ai’s gaze became distant, “You know…I recently heard that this trip was all about gaining power….”

She coughed, concentrating on stopping her blood from flowing out, “I hate it…think it that way…that all my experience…all my decisions…all my friend…nothing but stepping stones to gain some power. I loathe that reality from the bottom of my heart….”

“We are not stepping stones; even if we were only a small part of your journey, even if you had to leave, we would always be in your heart and memories! We will always be there!! So please! Don’t die!” Tanjiro screamed at the top of his voice, wiping his tears.

Rengoku let out a breath, a tear dripped from his eyes, and a smile appeared on his face, “Kamado is right.”

He raised her, putting her hand around his shoulder, “Kamado, holding her from that side!”

“Yes!!”

Rengoku took a step forward, with a happy grin on his lips, “We met! We met, and we fought, and we trained together! Because of you, I have gained a Greater Power! Does that mean that our meeting was my way of gaining more power?! That it was me being selfish! Dishonest?! No! Even if it was a meeting of fate! Even if it was arranged! I still feel that every moment I spent with you was true! So if this is a path you must walk, hold your head high and walk! As long as your heart is pure and true, nothing else matters!”

Ai’s eyes swelled up, her tears slid down her cheek, and a gorgeous smile appeared on her lips, “Rengoku…Kamado…It was wonderful…to have met you two.”

Rengoku felt her body go limp, and he felt his heart stop in that instance; his mind became blank when Kamado’s shout waved him up, “She’s alive! She has only fainted, but she is still subconsciously controlling her wounds! If we can make it! I know someone who can save her!”

Rengoku came out of the daze, and his gaze became fixed, “You are right! Could you take me to that person? We are going to save her no matter what!”
“Yessssss!!”

“Realllyyyyy Rengoku?!!! Leaving so soon?! We have just started to have fun!!”

Rengoku and Tanjiro froze, looking towards the flames from which Akaza walked out; his skin was still burnt, his wounds were healing as fast as there were flames between them, he had lost his right eye too, and yet there was a menacing grin on his face.

“You…are alive…?”

“Of course I am!! After all! This is the best fight! Rengoku! Because a Demon and I will save that girl! How about it?”

Akaza offered, clenching his fist, getting into a stance, forcing both of them in the corner, “Otherwise, I will kill you right here, and right now!”