A 7 year old girl is found dead in the local park's toilet. Kaga Kyouichiro, who was asked to find the girl, and his cousin Matsumiya Shuhei who's assigned to investigate the murder case, have to work together to crack the case. Their evidence lead them to the Maeharas, a family with parents, a son and a senile grandmother.

A man is stabbed to death in Tokyo's Nihonbashi area. The victim staggers with the knife still in the wound for eight minutes before collapsing under the winged statues of two Kirin on the famous Nihonbashi bridge. The suspect, on the other hand, is now in coma, having fled the scene and been hit by a truck. On hearing this news, his girlfriend, Kaori Nakahara, insist that he is innocent. The case falls to Kyoichiro Kaga, a brilliant detective. Kaga realizes that behind this apparently open-and-shut case is a tangled web of mystery involving both victim and suspect, and their families. What was the victim thinking as he died? Will Kaga unravel the mystery at the heart of the case?

A man is found dead in a office of Takayanagi Ballet Company. The suspect is a female dancer at the ballet company. The Takayanagi Ballet Company insists that the incident is a self defense case, but after an investigation there's doubts in that claim. Then, the director of the Takayanagi Ballet Company is poisoned to death. Are the cases related?

Michiko Oshitani, who lived in Shiga Prefecture, is found dead at an apartment in Tokyo. She was strangled to death. Mutsuo Koshikawa is the owner of the apartment and he goes missing. Detectives including Yuhei Matsumiya who is a cousin of Detective Kyoichiro Kaga , have difficulties in solving the case. They can't find a connection between Michiko Oshitani and Mutsuo Koshikawa. They soon learn that Michiko Oshitani came to Tokyo to visit Hiromi Asai . They graduated from the same school, but there isn't a connection between Hiromi Asai and Mutsuo Koshikawa. Detective Yuhei Matsumiya finds something near Michiko Oshitani's body. That something has the names of 12 bridges surrounding the Nihonbashi area of Tokyo. Detective Kyoichiro Kaga learns of the clue and becomes agitated. There's a connection with his late mother