Muichiro is a boy of fair skin complexion, short stature, and a lean-muscular build along with long straight hair of a raven-black color that fades to a cyan color as it approaches his waist. 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 possesses large, empty-looking cyan eyes. He is identical in appearance to his older twin brother Yuichiro. He is described as thinner and smaller than Tanjiro but deceptively strong.It is revealed that Muichiro suffers from amnesia caused by his distressing past. Many of his personality traits line up with the symptoms of PTSD. It would explain his poor memory, difficulty concentrating, and hypervigilance.

After the mission at Natagumo mountain, the hashiras learned that Tanjiro went on a mission with Nezuko, as it was strictly forbidden for a demon hunter to go on a mission with a demon, and Tanjiro He fainted And Cleanup Brigade Member He woke him up and robbed Tanjiro when he woke up, it was kagaya ubuyashiki mansion it's demon slayer corps leader he didn't realize who they were at first Tengen, Muichiro,Gyomei,Shinobu,Giyu,rengoku,Sanemi, Obanai were lying on the tree and Kaburamaru was around his neck And since Giyu didn't kill Nezuko, he was also considered guilty and was about to decide how Giyu's punishment would be, then he fell silent after Shinobu said that he came without making a sound Of course, while everyone was thinking about what the punishment would be, Muichiro's attention was constantly drawn to the bird above and the shape of the Cloud.

But then Sanemi came and Nezuko was sleeping in the box then he put his katana inside the box and stabbed Nezuko in the shoulder then he took it out and Tanjiro got angry at him and headbutted him but then Kagaya ubuyashiki When he came with his two daughters,Everyone fell at his feet and bowed respectfully to him.he read the letter and knew tanjiro is going missions with his sister And he said he accepted it The letter sent by Urokodaki And Kagaya's daughters read the letter and it said:"Nezuko hasn't consumed human flesh or blood for two years since she became a demon So accept it if Nezuko breaks this rule Urokodaki and Giyu will commit seppuku." But Sanemi was still not convinced, he cut his arm with a katana and smelled the blood of the nezuko smelled blood.Sanemi has a rare type of blood which was later revealed to be one of that is incredibly intoxicating to Demons. It is also unique due to its intense potency that the smallest whiff of his blood immediately causes demons to salivate, lose focus and go crazy for it Then he thrust it towards the mansion and thrust his katana in and out twice while Obanai jumped and pinned him to the ground with his elbow. When Nezuko came out, she was drooling and trying to control herself, but then she turned her face away in disgust and resisted the temptation Then they put Nezuko back in the box but of course Tanjiro was against his sister being stabbed three times so he came running immediately. And interrupted Kagaya Meanwhile Cleanup Brigade Members He was trying to stop Tanjiro.

tanjiro: "Let me headbutt this guy again. He stabbed my sister three times This man hurt Nezuko my sister!!"