Magical law exists to bestow punishment for crimes committed by spirits. Muhyo Toru, an executor of magical law, and his assistant, Kusano Jiro, work at the Muhyo Bureau of Supernatural Investigation. One day, a girl named Rie comes to them for a consultation about a spirit inhabiting the local train station, which she suspects is the spirits of her late friend Taeko.

Muhyo and Roji visit the home of Shiratori Aya, a client who says a black shadow has been playing her piano at 2:00 AM every night. Muhyo concludes that the shadow is a vengeful spirit born from countless people who envy Aya's talent, but in fact... Later, a package arrives at the bureau for Roji, containing a "magic-sealing pen" and an invitation to take an exam for a promotion to first-class secretary. Then Nana enters with a photo she took of a spirit on a pedestrian bridge...

Muhyo and Roji arrive at the Magical Law Association so Roji can take the promotion exam, and for whatever reason, Nana has come along with them. They're greeted by Muhyo's former classmate, Yoichi, who mentions a name that seems to strike fear into the hearts of those who hear it. The gang's concerns become reality when a spirit appears during the exam briefing...

Muhyo has taken care of the spirit that infects people through touch, but Roji feels he's to blame for the chaos it caused and takes off alone. Yoichi follows him and tells him a story from when he and Muhyo were attending the Magic Law School together - a sad story about the two of them and their friend Enchu, a kind, earnest boy who was working harder than anyone to become an executor.

Muhyo, Roji, and Nana visit a rustic hot spring resort to meet a client. They bathe in the hot springs while waiting for him... and then Roji catches a middle-aged man peeping into the women's bath at Nana. The man turns out to be their client and the author of a current best-selling novel series, "The Butterfly of the Night," Yontani Abeyuki.

Bico, a magical tools master who attended the Magic Law School with Muhyo, suddenly appears at the Bureau one day. Bico asks Muhyo to come to Magic Prison No. 18, a prison where very powerful spirits are sealed. A talisman that had been used to seal the bottom level, where the most dangerous spirits are kept, has been ripped off its door... and Bico feels responsible as the one who had made the talisman. Muhyo agrees on the condition that Bico will owe him one later, and they set off for the island that houses the magic prison.

Muhyo, Bico, Roji, and Bico's teacher Rio head down to the bottom level of the magic prison, a place swirling with ectoplasm. Many spirits lurk in the darkness since the talisman sealing this floor was removed. One of them, a Rain Dog, attacks the group, infecting Bico with a spirit virus. So Muhyo opens his magical law text and faces the Rain Dog...

The one who ripped the talisman off the bottom level of the magic prison was the spirit of a little girl named Sophie, nicknamed the Face Ripper. She has taken on the guise of someone in the magic prison using her ability to mimic others by stealing their faces. Just when they find out who she's turned into, Sophie reveals her true self... but Muhyo is still asleep after using too much magical law earlier. The others force him awake, but his only option to defeat the powerful Sophie is to use high-level magical law...

Magical tools masters normally can't use magical tools, but Roji realizes that Rio used one to protect Bico. Meanwhile, Muhyo has collapsed after exhausting his ren, leaving him in a dangerous condition of mental numbness... the exact moment Rio has been waiting for.

Rio continues her relentless attack on Muhyo and the others, refusing to even listen to the fervent pleas of her own pupil, Bico. Those who have sold their souls to a messenger of Hell using forbidden magical law can never be human again... but Muhyo says there may be something they can do for Rio. However, he needs to recover from his mental numbness in order to do it. Backed into a corner, the team gambles everything on a secret formula concocted by Bico to help him temporarily recover...

Enchu, the one behind all of Muhyo's recent struggles, finally reveals himself and challenges the gang to battle. The spirits released from the magic prison combine into one, and both Muhyo and Roji end up trapped within its fused body. What will come of Muhyo and Roji, and how will Muhyo's battle with Enchu end?!