Detective Conan - Season 1 Episode 697 : The Window of the Girls Academy

Kogoro was hired by Misaki Yanai, an old friend of Ran and Sonoko from middle-high school, to re-investigate the suicide of her older sister, Nagisa. Misaki believe that her sister didn't commit suicide but instead, was murdered. Kogoro then phoned Inspector Megure and was confirmed that it was indeed a suicide which make Misaki burst into tears. With Conan suggestion, Kogoro allow her to retell what actually occurred. As Nagisa had planned to marry Shibagaki after she finished high school, she has no reason to commit suicide. They later arranged for Takagi to share them the crime scene's photo.