Hiiyo Ikusaba

Vice-president of the first generation adventure club. He serve as the main antagonist of the story.

Ikusaba almost caused the disbanding of the first generation of Adventure club by using a female member as sacrifice to get a Nanana Collection, causing her physically crippling, and left the club with the collection.

Ikusaba is also the previous resident of Nanana's room, but was kicked out as he rarely stays and often left Nanana alone.

(Source: nanana.wikia)