Mushitarō Oguri possesses dark hair slicked leftward and yellow eyes with multi-ringed pupils. He typically dresses in a sharp green suit with a black bowtie and pocket square, though his appearance shifted during captivity by the Seventh Agency. Proud and demanding, he frequently displays arrogance regarding his abilities and shows minimal loyalty to groups like the Rats in the House of the Dead, viewing them as instruments for personal goals. When recruited by Fyodor Dostoevsky, he demanded specific conditions: a secluded Western-style house, occult books, fine china, and an escape plan. He harbors intense dislikes for dirt, thunderstorms, summer, and detectives, often incorporating foreign words into his speech. Despite his disdain for mystery novels, he writes them occasionally to process grief over his friend Yokomizo’s death, seeking to feel Yokomizo’s presence. Reminders of Yokomizo trigger emotional vulnerability, and he fiercely protects Yokomizo’s legacy. His ability, **The Perfect Crime**, conjures invisible organisms that erase all physical and digital evidence of crimes, including forensic traces and surveillance footage, capable of obstructing even exceptional deductive abilities like Ranpo Edogawa’s. During his student days, he befriended Yokomizo. As Yokomizo succumbed to gastric cancer, they collaborated on an "ultimate mystery" where Yokomizo requested assisted suicide. Mushitarō strangled Yokomizo at an inn, weeping during the act—teardrops stained the manuscript’s final page. He replaced the page with a photocopy and hid the original in a shop. Later, he anonymously sold the manuscript to Edgar Allan Poe for ¥20 million and staged his own death by dropping a disguised dummy from a tower to frame Ranpo Edogawa. Imprisoned by the Seventh Agency to cover government crimes, Mushitarō was freed by Fyodor in exchange for aiding the Rats’ "Cannibalism" operation. During this period, Ango Sakaguchi tasked him with erasing Osamu Dazai’s Port Mafia criminal records using his ability. He also forged military police documents leading to Doppo Kunikida’s arrest. After Fyodor’s capture, Mushitarō surrendered. Nikolai Gogol intercepted his transport, kidnapped him, and tortured him to reverse **The Perfect Crime**’s erasure of Dazai’s records, reinstating evidence against Dazai. Rescued by Atsushi Nakajima and Kyōka Izumi from a high-security bank, he shared intelligence about the Decay of the Angel with them despite distrusting Ango. He now resides in Edgar Allan Poe’s mansion, writing mystery stories while mentally conversing with Yokomizo.