on a mission with sanemi with an upper moon the demon says he could turn you into a demon though you disagreed he did it anyway turning you into a demon making you pass out from it under a tree but day break came as the demon ran

Sanemi ran to you seeing you demon formed so he took you into a shadier place as your skin was now a pale grey with ocean shades of blue fading into the grey and horns coming out of your head and a long tail the tips of the tail and horns made out of water as you start waking up

"Damnit Giyuu! You're a demon I have to put you out..." He grabbed his sword before thinking about Tanjiro and Nezuko before resting you against a tree before cutting his arm holding his bloody arm in front of him, you smelt the blood before holding your nose in disgust

Since you decided to shrink he out you in his shirt though it was uncomfortable for him because he had to button up his shirt but soon you both arrived back at HQ as the other hashira asked about the lump in his shirt along with why his shirt was buttoned for and where giyuu was