In most ordinary high schools, numerous stories and rumors circulate—some scandalous, some happy, and some... more macabre. One such example involves monsters lurking in an abandoned mansion outside of town. Such tales, however, prove too tempting for Hiroshi and his friends Mika, Takeshi, and Takurou to resist. They decide to brave the rumored dangers to investigate the manor and complete a test of courage. Each of them approaches the mansion with an overwhelming sense of dread. And when they enter, they encounter a blue monster named Ao Oni who attacks them. As Hiroshi and his friends attempt to solve the various puzzles in the mansion and escape their new blue nemesis, they find themselves meeting several horrible endings as they fail miserably.