Ch. 507Kokushibo!
Gawain helped Yoriichi recover his resolve by reminding him that his life had not been meaningless. Yoriichi pledged to hunt Muzan Kibutsuji and set out immediately to confront his demon elder brother, Kokushibo.
- Gawain comforted Yoriichi, whose memories of the Kamado Family's kindness helped him regain hope.
- Yoriichi recalled the deaths of Uta and their child, his years fighting demons alongside Michikatsu Tsugikuni, and Michikatsu's betrayal of the Demon Slayer Corps.
- Yoriichi revealed that his elder brother had become a demon, murdered people, and sometimes waited for Yoriichi to find him.
- Yoriichi asked Gawain to let him pursue his brother at once, warning that demons might learn of their battle near Shinano and hide.
- Though Gawain questioned whether Yoriichi was strong enough to fight, Yoriichi insisted he could still kill his brother and named him Kokushibo.