Board Thread:Fun and Games/@comment-25084221-20160903081409/@comment-26404599-20160903162910

Ah I see, well this confirms further suspicion, obviously we'll never know of Sonosuke's type of reaction after Seiko's death but if there's anything to go on, he obviously told Ruruka about the secret door and maybe wanted to make an exit to the game as quickly as possible. The fact Ruruka stabbed Sonosuke with the same knife used on Seiko could also mean Sonosuke told her about where the dead Seiko was after they met up.