Yuichiro was a short young boy with long, straight hair of a raven-black color that fades to cyan the closer to his waist it goes. He wore it loose with two clumps protruding slightly from each side of his head, a set of marginally shorter hair left down to frame his face, and unruly bangs over his forehead. He also possessed large, cyan eyes, a trait, like his hair, that he shared with his twin brother Muichiro. In the past, their house was attacked and Yuichiro stepped in front of the demon to protect Muichiro and lost his arm, but even though he died, he was revived thanks to muzan inject his blood blood, but he he become demon.

Muichiro didn't care that his brother yuichiro a demon . he's still his brother and he's not going to let him go.Even though protecting a demon was against the Demon Slayer Corps, Muichiro could not kill his own brother.

He carries Yuichiro through a village while he is in in a wooden box on his back. He's silent and he could guess that he was staring at the clouds or just spacing out like normal.