Got stronger before starting

Entering as a young child, Banjiro learned from his father and worked tirelessly to awaken as a Sun Hashira while also putting the moves on Kie Kamado and Banjiro's new siblings. He never went over the line, but his family relied on him and looked at him differently as he constantly put on the moves in place of their father, who was sent to the Demon Slayer Corps and Tamayo to receive medical aid. But things couldn't remain as they were; Banjiro needed to let Muzan wreak havoc so he could give Nezuko and Banjiro the starting jump they needed. Thus, with that in mind, Banjiro had his family sent away as Muzan arrived to see a bunch of fake graves, believing Nezuko was the last of the bloodline before turning her into a demon. Once transformed, her transformations began as Banjiro had wished, making her bigger and stronger as Banjiro made his way back home to find his sister filled with uncontrollable bloodlust. The two would then get into a fight as Nezuko tried to kill him and rip off his pants, eventually getting interrupted by Giyu, leading Nezuko to try and protect Banjiro, causing her to be spared and put into a box as her form shrank.