Farewell, space invaders! Momo and the gang finally set out to find the second Okarun ball! To gather information in peace, they decide to found a club for cultural and historical studies. But the teacher who volunteers to supervise them, Mr. Sanjôme, seems suspicious... As he sets up the “club” room, Okarun runs into his class representative who gives him a revelation: since the day she picked up a strange golden ball, he has sometimes seen her in the appearance of a dark “canon vampire.” She also sometimes feels an overwhelming weight on her back... Could this phenomenon be related to an event from her past?