Mahiru Yanase is burdened by a belief in the law of equivalent exchange: every positive event in her life is shadowed by misfortune. Constantly overshadowed by her kinder twin sister, Mayo, Mahiru resigns herself to this pattern of bad luck. But when the charming Aoi Satomi shows a romantic interest in her, Mahiru's world is thrown off balance. Cynical of Aoi's sudden affection, Mahiru anticipates impending disaster. Yet, Aoi's presence might just hold the key to reversing Mahiru's streak of ill fortune.