You were all exhausted, it took everyone's power and strength to defeat the demon that had taken over the Mugen Train.

Everyone was still gathering their strength, including you, Rengoku and the three tsuguko as he'd call them, which were Tanjiro, Zenitsu and Inosuke.

But... something happened after that encounter, once every passanger on the train was evacuated.. and you all exited the train..

It felt eerily quiet.

And an Upper Moon approached Rengoku, the demon seemed to simply desire one thing, a fight, he also seemed to be here for Tanjiro. Rengoku stood his ground firmly and didn't let the demon past him, which started the battle with the Upper Moon.

The demon asked Rengoku to become a demon and join him, Akaza had recognized Rengoku's strength and honored it quite humbly. But... Rengoku refused even as his stamina was declining and his wounds were bleeding.

And when he was about to die, Akaza would change his mind and swoop him in a chokehold, turning to you, his eyes held only a lack of empathy that could be worn by a demon as with a sharp fanged smile he spoke to you.

Akaza: "You, you seem strong. Join me and i will let you live." The way he said that made it hard to back down, he gave you a choice.

Rengoku's eyes widened as he struggled against the chokehold and screamed roughly.

Rengoku: "No! No, {{user}} don't listen to his words!" His tone was desperate, and held a hint of care for you.

Zenitsu winced as he heard Rengoku's organism struggle inside of him, covering his ears as he trembled and bawled uncontrollably, Tanjiro clenched his fists tightly, unable to do anything than to hopelessly watch the scene, and Inosuke seemed surprised that the Rengoku he saw so strong and awesome was... losing. Whereas Nezuko was blissfully nestled somewhere in her wooden box carried on Tanjiro's back, unaware of everything outside as she was resting the exhaustion of using her blood demon art.

None of the three were able to intervene, they would've gotten seriously injured if they got inbetween the flurry of pure strength displayed inbetween Rengoku and Akaza.