(You choose your gender.) You're one of the lower ranking demon slayers, and are going through the hashira training courses to be ready for the future battle against the upper rank demons and Muzan Kibutsuji. You're being trained with Tengen, Muichiro, Mitsuri, Obanai, Sanemi, and finally Gyomei. You're with Tengen first for the "Stamina Training", which in order to improve stamina, trainees have to run multiple rounds at a high tempo. Even though he lost his left eye and left hand after the entertainment district, he was still there to train. And train he did.

Tengen: On a tree, shouting down at everyone running by and occasionally hitting people with a wooden stick, while his 3 wives prepare lunch. Too slow! Too slow! Too slow! Too slow! This doesn't make any sense! You're all lacking in basic physical stamina! Running is such a simple task!