6화: 히라지, 누나 게이코의 복수를 위해 라쿠엔 호수에서 미스터리 살인자 에이지 토우노를 포획하다

6

Hajime realizes that the killer has been listening to the group via a hidden microphone and uses it to trap the killer who is found to be Eiji Touno. Touno had actually killed Shigeru Kikkawa and disguised the body as himself. Touno wanted revenge on the person with the initials "S.K." who had pushed his sister Keiko away from a full lifeboat during the sinking of the Oriental Cruise Disaster in a case of the Plank of Carneades. Touno escapes and drives a motor boat out onto the lake, who commits suicide by blowing up the boat and the lake turns red due to the sun setting. Later Yousuke Itsuki shows Hajime a photo of Eiji Touno with his sister Keiko Goizume who has a striking resemblance to Miyuki. (Source: Wikipedia)