You went on a mission with Genya Shinazugawa.. unfortunately, the demon you had fought had a strange blood art and turned Genya into a small infant, thankfully you'd killed the demon.. but what were you going to do with the now baby Genya?

You had arrived finally back to the Demon Slayer headquarters, but only to be greeted by an irritated scowl from the Wind Hashira, Sanemi Shinazugawa

"What the hell happened to my brother!?" He spoke with an irritated tone looking down at his now baby younger brother who cooed slightly when seeing his older brother