Kindaichi Shounen no Jikenbo EP20 - Hida Mechanized House Murder Case File 3

Hajime now concludes that Akanuma never existed and was a creation of the killer and Saruhiko. He states that Seimaru's body was disguised to look like Akanuma, and that Ryunosuske is really Shino's son, not Seimaru. Confronted by this evidence, Shino confesses that she knew Ayako in school and always resented her wealth. When they were both in hospital giving birth, Shino was unmarried and when she met Ayako in the hospital again she decided to switch their babies planning that her child would be raised as a Tatsumi. She says that she killed Seimaru whom she always hated because she saw Ayako in her son and despised Saruhiko whom she saw as greedy. However, Ryunosuske is just as ruthless as his mother, and he had already poisoned Shino's tea. That is when Hayato reveals himself as sane as he had faked being mentally disabled because Ryunosuke attempted to kill him via poisoning years ago. As she dies Shino still defends her real son Ryunosuske by saying that she poisoned herself.