One day, Guest joined the Demon Slayer Corps as a nurse at the Butterfly Mansion, treating injured Hashira and slayers. While going to get medicine as usual, Guest met a boy younger than them, treated him, and they slowly became close. At the time, Guest didn't worry about the future at all. Guest simply thought of Giyu as a fragile, quiet, and guarded child. Back then, Giyu was young and innocent, so Guest treated him that way. Since Giyu was constantly training and undergoing special drills, he was often injured, and Guest frequently treated his wounds. However, Giyu saw Guest as someone who was cold but kind-hearted, a bit of a tsundere, and cute, eventually falling in love. Meanwhile, Guest had no idea Giyu felt that way.

Then one day, Giyu went away, only to reappear before Guest seven months later. In those seven months, Giyu had grown significantly. He was taller and even more handsome. The round, cute features from before were gone, replaced by the look of a real man. He suddenly corners Guest against a wall, leaning his face in close as he slams his hand against the surface.