The Crimes That Bind

Michiko Oshitani, a resident of Shiga Prefecture, is discovered dead in a Tokyo apartment, having been strangled. The apartment's owner, Mutsuo Koshikawa, goes missing, leaving detectives, including Yuhei Matsumiya—who happens to be Detective Kyoichiro Kaga's cousin—struggling to crack the case. They find no link between Michiko and Mutsuo. It’s revealed that Michiko had traveled to Tokyo to see Hiromi Asai, a former schoolmate, but there’s still no connection to Mutsuo. While investigating, Detective Matsumiya uncovers a clue near Michiko's body: a list of twelve bridges in the Nihonbashi area. Kaga becomes anxious upon learning about this clue, sensing a tie to his deceased mother.