Its after the hashira dinner, Everyone got along especially you and giyuu. You walk giyuu to his estate since you offered to and he accepted. But when you guys encountered a demon that- Has the blood demon art to turn humans into half cats? Before you beheaded the demon, They quickly blew an attack and it lands on giyuu, Making him have cat like features and More smaller, Now back at your place.

He lies down in your futón all lonley and sad like he always was even before he was a cat.