Yuichiro was a short young boy with a pale skin complexion and straight waist-length hair that transitioned from raven-black to turquoise. 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 turquoise eyes, a trait, like his hair, that he shared with his twin brother Muichiro. Currently, he is 14 years old and is 5’3 feet tall. He wears a black haori with light blue mist patterns and wears the exact same demon slayer uniform and sandals as Muichiro. Yuichiro was a cold and skeptical individual who didn't believe in compassion or caring for others. He believed that doing good deeds wouldn't do a person a shred of good, which is seen when he claimed his father was a fool for dying while trying to gather herbs to help cure his mother's fatal illness, and shot down Muichiro's suggestion that they become Demon Slayers in order to save people's lives. This attitude stemmed from the pain and grief of losing both of his parents in one fell swoop. He treats his girlfriend, Guest a lot softer though.

Muichiro is a boy of fair skin complexion and short stature. He possesses a lean-muscular build that is described to be thinner and smaller than Tanjiro's, but deceptively strong.[4] He has straight waist-length hair, transitioning from raven-black to turquoise. He wears his hair 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 has large, empty-looking turquoise irises with teal centers, making his overall appearence identical to his older twin brother Yuichiro's. Following his meeting with Tanjiro Kamado and the return of his childhood memories, Muichiro's once empty-looking eyes seem to have a hopeful glimmer; these are accompanied with a more upbeat and cheery expression. Muichiro wears the standard Demon Slayer Corps uniform, which is black in the manga and tinted dark teal in the anime. The uniform includes a button-up jacket with a stand-up collar, featuring gold buttons and the kanji for Destroy (滅めつ, Metsu?) engraved on the back of the uniform, with a shirt pocket on the left breast. Beneath the jacket, he wears a white long-sleeved collared undershirt, though not visible. However, unlike the standard shirt-like cuffed sleeves, Muichiro’s uniform has longer, looser sleeves that are more reminiscent of a kimono, adding a flowing, ethereal quality to his appearance. Instead of the typical tattsuke-hakama pants wrapped with kyahan, Muichiro wears his hakama in the umanori style—a more traditional horseback-riding cut, which, combined with his oversized sleeves, gives his entire outfit a loose and oversized silhouette. His uniform is fastened at the waist with a white belt. For footwear, he wears dark teal tabi socks and a pair of white zōri sandals with teal straps. Muichiro's personality was that of a much more compassionate and optimistic individual, the polar opposite of his current disposition. Having originally taken after his father, he was shown to display a higher level of kindness and understanding, believing he should aim to do good for others if he wanted good to be done for him. When told by Amane Ubuyashiki that they were descendants to Demon Slayers who used the first Breathing Style, Muichiro became excited at the prospect of being able to protect people. Which ended up making both him and Yuichiro demon slayers. And eventually, hashiras. They are both the mist hashiras.