Yuichiro Tokito

Yuichiro is a small boy whose straight hair, reaching his waist, fades from black into turquoise, worn loose with untidy bangs, and his large turquoise eyes, like the hair, match those of his identical twin Muichiro. For clothing he wears a sleeveless robe carrying a faint blue mist pattern, much like the garment his twin had on at age ten.

Outwardly he is cold and cynical, dismissing kindness and good deeds as pointless and calling their father a fool for dying while gathering herbs for their sick mother. This bitterness grew from the grief of losing both parents at once, yet his final moments, spent praying for his brother and apologizing for holding him back, reveal that deep down he genuinely valued the good others do.

The sons of a woodcutter and his spouse, the brothers were orphaned at ten when illness took their mother and their father fell from a cliff fetching medicine in a storm. Muichiro inherited their father's warmth while Yuichiro hardened into detachment. When Amane Ubuyashiki came to recruit the boys as descendants of powerful slayers, Muichiro was eager but Yuichiro angrily refused and drove her away each time she returned.

That summer a demon attacked their cabin at night. Yuichiro threw himself between it and Muichiro, losing an arm in the process. Enraged by the demon's taunts, Muichiro destroyed it with whatever he could grab, and by dawn it crumbled to ash. Crawling back inside, he found his brother dying and praying for his survival.

With his dying breath Yuichiro admitted he had always known what the Mu in his brother's name truly signified, explaining that it represents infinity and that, when acting for others, he could call upon limitless strength. He then died holding his brother's hand. The loss became the fuel for Muichiro's rise into a powerful slayer and eventual Mist Hashira.

When Muichiro himself later dies after fighting Kokushibo, the twins reunite in the afterlife, where Yuichiro tearfully scolds him for dying young before they accept each other in an embrace. Long after, the pair return to life together as twins in present-day times. As an ordinary boy, Yuichiro had no combat abilities, and the first character of his name, meaning existence, stands in deliberate contrast to the nothingness in his brother's.