Mushitaro is a young man with dark hair slicked over to the left of his forehead. The pupils of his yellow eyes consist of several rings. He is very expressive. He dresses sharply, wearing a neat, fitting suit.
Mushitaro is a somewhat stuck-up man who takes pride in his ability. He is not a particularly loyal member of the Rats, saying that it only serves to fulfill his own goals. For example, when he meets Fyodor Dostoevsky, he demands a base of operations all for himself, including a bookshelf with occult books and fine china tableware. He is a formidable opponent against Ranpo Edogawa due to his ability. However, he easily breaks when his old friend Yokomizo is brought to mind.
He is interested in occult practices, and occasionally blurts out sentences related to it.
Mushitaro's ability, The Perfect Crime (完全犯罪 Kanzen Hanzai?), allows him to erase any evidence of a crime perfectly. It takes the form of small, invisible creatures coming out of his body and tampering with objects. It can cause even a great detective like Ranpo to get stumped. Hence, he refers himself as the infallible "detective killer".
Initially, he was a captive held by the organization called The Seventh Agency, exploiting his ability in order to cover up their crimes. Later on, Dostoevsky managed to break into his room, killing all the guards in order to set him free. In exchange for his freedom, Dostoevsky asked Mushitaro to help the Rats in the House of the Dead in their cannibalism strategy.
Mushitaro then agreed upon several conditions: first, that he neither will not appear on the front lines nor lift a hand. Another thing that Dostoevsky must provide a bookshelf, containing books about occultism and ancient alchemy and for all communication to be done via text messages. His hiding place must be comprised of a western-style house, far from the sea. Dostoevsky must provide him silver or white china tableware and starched clothes, and ultimately Dostoevsky must agree to assist in his escape to another country one week after the operation has done.
Ranpo is about to examine a suicide case, which in fact isn't a suicide at all, but on the other hand, is a murder case in which he suspects as the way "the cleaner" camouflage himself, Mushitaro then appears in the background, activating his ability, thus erasing all the evidence of the crime. As Ranpo uses his ultra-deduction on the victim to locate Mushitaro's location, he suddenly looks up at Edgar Allan Poe with a worrisome look, stating that he doesn't know anything since there is not a single trace of evidence left by the murderer. Mushitaro then self-proclaims himself as the "detective killer", saying that there is no way Ranpo can prove Doppo Kunikida's innocence. He then allegorizes the action of getting away with murder is like taking candy from a baby, just like what he has done to someone he referred to as "that guy" which he killed several days ago.
As he succumbs in his own self-glorification, Ranpo tugs his shoulder from behind, asking Mushitaro where the taxi stand is. Mushitaro, who is currently waiting for the extractor's vehicle looking evidently troubled as Ranpo may suspect anything if he were to see the extractor. In order for the plan to go smoothly, Mushitaro assigns Ranpo to a train station five minutes away from them, which Ranpo then refuses, plainly stating his distaste for walking.
Not wanting to lose his calm, Mushitaro then tells Ranpo to catch a bus that's heading to the station when it approaches the bus stop nearby. Ranpo then abruptly exclaims that he doesn't know to ride the train or even the bus. Therefore, he requests Mushitaro to let him ride on his back. At that moment, the extractor has arrived. Mushitaro bid Ranpo a farewell as he enters the car. The car is headed towards Yokohama smuggling harbor, in which Mushitaro uses to escape the country.
Mushitaro, being too preoccupied with his mind is oblivious to the fact that Ranpo has entered the car and is currently sitting beside him. In exchange for letting him ride in the car, Ranpo promises to offer Mushitaro some job if he were to lose it. He then tries to avert Ranpo's attention by asking about him meanwhile the car is headed to the station. Ranpo tells Mushitaro about Kunikida false charge and the "falling murder" he witnessed earlier. Mushitaro, pretending to not know the murder case, absent-mindedly states that he isn't interested in either detectives or murder. Ranpo replies that it is only natural that the case is so difficult because after all the culprit has a "reality-altering" type of ability. He freezes as he is surprised at how far Ranpo has gotten. But then silently agrees when Ranpo states that his deduction is, after all, just a technique, thus cannot fight reality-benders as no detective's reasoning can overcome the laws of reality. But as in this case, Ranpo states that he managed to solve it.
Ranpo then elaborates his reasoning behind the case, connecting the "falling murder" case to the recent "Kindaichi murder" case of an author. He deducts that "the cleaner" and the author's murderer are both the same person with the copied manuscript as its proof and Mushitaro being the culprit in both cases.
- (to his victim) "Death. It's a spasm. Murder. It's the worship of the weak. I am the angel of murder, the king of criminals. Requeiscat in pace!"
- (to Ranpo Edogawa) "The ethereal gate closed! It won't open again! I am the absolute infallible detective killer!"
- (to Fyodor Dostoevsky) "With tyrants and demons, I'll make deal with a demon. That's in my nature."
- (to Ranpo Edogawa and Edgar Allan Poe) "Kneel detectives! I am the king of crime! No one can force me to sin and repent!"