A genius physicist nicknamed 'Galileo'. He is Ishigami's college classmate and one of his few rivals. He pursues the truth of the case with exceptional logic and observation skills. He values reason and evidence over emotion. He experiences deep conflict between friendship and the truth. "Which do you think is harder: creating a problem that no one can solve, or solving that problem?"

A woman who works diligently at a lunchbox shop. She is a single mother raising her daughter Misato alone. She suffers from constant threats and harassment from her ex-husband, Togashi. Her life is shaken to its core by an accidental murder. She becomes involved in the case while receiving help from Ishigami.

Yasuko's ex-husband. He has lived an irresponsible life, causing trouble with alcohol and money. Even after the divorce, he seeks out Yasuko to threaten and abuse her. He visits her house on the day of the incident to demand money. His actions become the catalyst for everything.

Yasuko's only daughter. She cherishes and relies on her mother more than anyone. She gets caught up in the incident during Togashi's violent outburst. She is deeply traumatized by the sudden tragedy. She stands at the center of the case alongside her mother.