A boy detective. He was apparently a high school detective once, but it's a secret from the world that his body shrank due to some kind of drug. For some reason, he gets caught up in murder cases wherever he goes and has solved numerous incidents. He conducts investigations using inventions from a professor and corners culprits with sharp deduction. He does whatever he wants, such as using a stun-gun wristwatch to make deductions through the people around him. He happens to be staying at the Ota Hotel.

A high school detective. For some reason, he is often caught up in murder cases wherever he goes and has solved numerous incidents. His grandfather was the famous detective Kosuke Kindaichi. He finds the culprit with sharp deduction. In crucial moments, he drops his signature line: "I swear on my grandfather's name!" He happens to be staying at the Ota Hotel.

Akira Ota 60s. A man with slicked-back hair, a mustache, and a sharp gaze. The manager of the Ota Hotel. The Ota Hotel is a mountain resort hotel boasting a Western-style exterior and 150 years of history. Many guests stay for winter sports during the season, but the area can be hit by blizzards so severe that going outside is impossible in bad weather. He has a track record of turning the business around after it nearly failed, but there are rumors he used aggressive tactics against neighboring companies at the time, and he seems to have earned people's resentment.

Takeshi Sato 30s. A male corporate executive. He exudes the aura of a capable, high-achieving businessman. He is staying at the Ota Hotel for business negotiations.

Manami Suzuki 20s. A female ski instructor with a cheerful personality. She is staying at the Ota Hotel.

Yujiro Tanaka 40s. An office worker. A large, stout man who is a heavy eater. He is staying at the Ota Hotel for business negotiations with Takeshi Sato.

Mai Sasaki 40s. A CEO's wife. A beautiful woman with a good figure, but she has a proud and arrogant personality, and her relationship with her husband, Takao Sasaki, has grown cold. She is staying in a suite at the Ota Hotel with her husband for a vacation.

Takao Sasaki 50s. A CEO. A stern-looking man with salt-and-pepper hair and glasses. He is staying in a suite at the Ota Hotel with his wife, Mai Sasaki, for a vacation.

Ichiro Takahashi 20s. A handsome office worker. He is staying at the Ota Hotel on vacation. He has feelings for the ski instructor, Manami Suzuki, but he doesn't feel good seeing her being friendly to other guests.

The perpetrator of the incident, one of the characters. Until the culprit is revealed, care is taken to keep them unrecognizable as a figure entirely in black.