After seeing helpless the fall of Nohara and Kamizuki, Eight and Sans Nom continue their perilous road leading to the best observation post of the girls' dormitory bathroom. But Eight falls into the pool and is discovered by Ayame. Once this event passes, Eight will go from surprise to surprise by discovering the mysterious past of Sans Nom, then by making the meeting of the legendary monster of the basement of the school, which will make him a surprising revelation about his father.