Muichiro is a young man of short stature and light complexion. He has long black hair which fades into a mint green color. He has a fringe covering his eyebrows. Two strands of hair frames his face while the remaining is tucked behind his ears. His eyes are the same as the ends of his hair; mint green.
He usually wears the Demon Hunter uniform with a few modifications. The sleeves of his uniform are flowy and reminiscence of a kimono sleeve instead of the standard cuffed uniform. His pants are the normal standard hakama pants which he lets loose without tucking it into a piece of fabric thus having the appearance of a loose fitted uniform.
Muichiro is an air-headed individual who seems to constantly wander off in thought and never focus on one thing. However, he has been shown to get serious at times and is devoted to his work as a Demon Hunter and the Mist Pillar. Impassive and at times obtuse, Muichiro tends to think only for himself and operates on logic alone.
Muichiro's original personality was much more caring and kind having taken after his father. Despite this, he always held an omnipresent rage deeply suppressed inside of him that inevitably drove his training. After his memories returned, he started expressing more emotions and became more confident in himself. He also learned other expressions such as displaying sarcasm and smugness towards the fifth upper moon, Gyokko.
Muichiro and his twin older brother, Yuichiro, were born to a woodcutter and his wife. While they were 10, their mother caught a cold. It eventually turned into bronchitis and killed her while in bed. Their father, away at the time, went to fetch medicinal herbs during a storm and wound up falling off a cliff to his death.
The two siblings survived together. While Muichiro took after the emotive and kind nature of their father, Yuichiro instead held a cold and impassive outlook. They often bickered and Muichiro considered being with him a living hell.
In the following spring, Oyakata's wife Amane arrived to recruit them for the Demon Killing Corps. Muichiro's excitement was opposed by Yuichiro's unwelcoming and rejecting reception. In an outburst, Yuichiro revealed that he blamed the death of their parents on their hardworking and selfless nature and adopted a cold outlook hoping to keep himself and his brother alive.
While Amane continued to visit the twins, Yuichiro chased her away each time. In the following summer, a demon arrived at their cabin. Yuichiro lost his left arm defending Muichiro. As the demon badgered them for their worthlessness, Muichiro lost himself in rage and destroyed the demon with all the tools at their disposal and wooden logs.
By sunrise, the demon withered into ash and Muichiro dragged himself back to the house. There, he found Yuichiro near death praying to the heavens that his brother might survive. He laid there grasping his brother's hand as the latter died and he slowly withered away. Amane and her daughters later arrived to heal him.
Afterwards, Muichiro would lose his memories and serve the Demon Killing Corps. He quickly rose to become a pillar while his memories would remain lost until battling in the Swordsmith Village. With his memories gone, he began taking after Yuichiro's personality. He met Kyojuro Rengoku during this period in the Demon Killing Corps who told him to do the best they could as pillars.
His first blades were made by Tetsuido up until a heart attack that led to his death. Kanamori, following Tetsuido's techniques, created Muichiro's current blade.
Abilities and Powers
- Enhanced strength: Despite his build being the smallest and seemingly weak of the Demon Hunters and Pillars, Muichiro has been shown to be stronger than Tanjiro Kamado by a wide margin. He did not budge when the latter held on and gripped his arm with all of his strength, despite Tanjiro being strong enough to break Genya Shinazugawa's arm even before he began training as a Demon Slayer.
- Omnipresent Rage: Muichiro attributes the origin of his willpower towards training and strength towards the awakened rage within him.
- Demon Slayer Mark: First awakened during his battle against Upper Moon Five, Gyokko. The mark appears as several red cloud/mist-like designs which cover the entirety of his body. While the mark is active, his offensive and defensive abilities are increased by several times their usual strength. The power increase was enough to grant him the strength to not only operate a severely poisoned body, but effortlessly kill an Upper Moon as well. However, once the mark vanished he immediately began suffering from the effects of the poison; showing that the mark is only effective for as long as it is manifested.
Breath of Mist Style (
- First Form: Hanging Sky, Distant Mist (
壱ノ 型 垂 天 遠 霞Ichi no kata: Suiten Tōgasumi?)- A straightforward thrust attack.
- Second Form: Eight Layered Mist (
弐ノ 型 八 重 霞Ni no kata: Yaekasumi?) - Muichiro unleashes multiple slashes one on top of the other in quick succession.
- Third Form: Demisting Blast (
参ノ 型 霞 散の 飛 沫San no kata: Kasan no Shibuki?) - A circular slash that blows away projectile attacks from enemies.
- Fourth Form: Advection Slash (
肆ノ 型 移 流 斬り Shi no kata: Iryūkiri?) - A quick slash from the sheathe reminiscent of an Iaidō technique.
- Fifth Form: Sea of Clouds and Haze (
伍ノ 型 霞 雲の 海Go no kata: Kaun no Umi?) - Muichiro charges towards an enemy attack at high speed and unleashes a flurry of slashes.
- Six Form: Moonlit Mist (
陸ノ 型 月の 霞 消Roku no kata: Tsuki no Kashō?) - Muichiro leaps high in the air and sends a series of countless ranged slashes downwards.
- Seventh form: Obscuring Clouds (
漆ノ 型 朧Sachi no kata: Oboro?) - A technique in which Muichiro drastically changes the tempo of his movement to disorient an enemy. When he shows himself, his speed will appear to be extremely slow but when he hides, he moves in the blink of an eye.
- The "Mu" (無) in his first name, Muichiro, contains the same kanji for "In" in "Infinity" (無限). When written as a single kanji, it can mean "Nothingness."