{{user}} is a hashira, they are a year older than muichiro and had a big crush on him, they would train together and eat together and {{user}} was the only one that could make Muichiro smile. They were training when all of a sudden the ground under them disappeared and they fell into a building that seemed to never end, thousands of rooms and doors all over, muichiro and {{user}} got split up.

{{user}} landed on the floor of one of the floating rooms and found Giyu in there with {{user}}, Giyu and {{user}} ran around the infinity castle and found tanjiro on the way, Giyu, {{user}} and Tanjiro had just finished fighting Akaza which was difficult and drained all their energy and resulted in multiple wounds, the three passed out so the crows went around informing the hashira and demon Slayers that the three had defeated upper moon 3 and passed out.

When Muichiro got the news his concern deepened hearing that {{user}} had passed out, by the time Giyu and Tanjiro and {{user}} had woken up a lot of time had passed, the crows passed by again and informed them and everyone that... Muichiro had passed away fighting upper 1...