The Metropolitan Police Department is struggling to investigate a series of murders, yet Detective Isshiki is ordered to go home. Kiku of the General Affairs Division sends him to meet a certain sleuth—a shaggy-haired eccentric named Kamonohashi Ron.

Ron is excited to solve cases by using Toto, but he's not on any good ones because his boss thinks he's useless. All he gets are odd jobs and busywork. Ron, however, is quite interested in a new report about coins going missing from a piggy bank...

Ron wins a pair of tickets to a hot spring in a raffle. Toto accompanies him to stay at the Benizome Inn. The innkeeper who greets them is friendly, but he isn't who he seems. Plus, it isn't long before Ron's eccentricities begin to surface.

There has been a murder. Ron listens to the other guests' testimonies and begins his deductions. Spitz secretly rejoices at this chance to catch Ron in the act of sleuthing, but outwardly both he and Amamiya entrust the investigation to Toto.

Kawasemi Omito, a supremely skilled detective, leads a joint investigation into a serial killing case. Amamiya lends him Toto, whom Kawasemi deems so useless he's invisible. Ron appears at the newest crime scene as a consultant, irritating Kawasemi.

Ron loves a certain TV show that puts psychic abilities to the test. During a live broadcast, a psychic claims he can control minds with written words. His neurosurgeon opponent refutes his claims. Then, the psychic writes the word "Death" on a card.

Toto and Ron are invited to a meteor shower viewing being held on Nandan Island. Also invited is John Grizzly, an instructor at BLUE. There was a murder at the observatory years ago, so the director has brought in first-rate detectives...just in case.

Ron is named main suspect in a murder and Toto investigates to clear his name. Everyone but Ron has an alibi for the time of the murder, which only seems to cement his guilt, but Toto discovers a few things that cast a new light on the incident.

Toto gathers everyone together and explains the truth behind the murders. With their name exposed, the culprit takes drastic measures not to be caught, but not before revealing that there's more to this incident than anyone imagined.

Toto is shadowed by a reporter who's a huge fan of his for the way he's solved one difficult case after another. They step into a cafe where Ron happens to be working, making things a little awkward. Then, a customer collapses to the ground—poisoned!

Ron agrees to take on Spitz's search request in exchange for his obtaining a file on the Bloody Training Incident. Spitz accepts Ron's terms and takes Ron and Toto to Yadamura, a village in Yamanashi prefecture where his ethnologist brother disappeared.

Toto reveals the truth of the case and the culprit admits to their crimes. Ron's disorder triggers, putting the culprit in danger, but help comes from an unexpected source. Who is their last minute savior, and how are they connected to everything?