Nanatsu no Hikan (七つの秘館, Literally: Seven Mysterious Mansions) is a three-disc adventure game produced by Shibusawa Kou. It is one of the few adventure games from Koei to feature 3D models for its characters. The game is set in a contemporary setting, roughly taking place in the mid or late nineties. Even so, there are several historical references within the game's puzzles.