GJ Club

Shinomiya Kyouya is forced to become a new member of the GJ, an unidentified club that dwells in a room of the former building of a certain school. Here he meets the club leader, Mao, a short girl with a big attitude; Mao's younger sister, Megumi, who has the heart of a bipolar angel; the recognized genius with a lack of common sense, Shion; and the always-hungry and mysterious Kirara. Time flies with these unique girls around.

(Source: MyAnimeList)