kyokobaka

Otonokizaka High School stands on the border of three cities: Akihabara—a pop culture mecca that's evolving by the minute; Kanda—a conservative, cultured city where history and tradition reign supreme; and Jinbo—a quiet area reserved for a more mature, sophisticated population. Amidst this culture clash, the school now faces closure due to the enrollment of fewer and fewer students.

Yukiteru Amano (or Yuki) is a loner who never really interact with people and prefers writing a diary on his cell phone with his only companion being an imaginary friend named Deus Ex Machina, the God of Time and Space. However, Yuki soon learns that Deus is not a figment of his imagination but real when Deus makes him a participant in a battle royale with eleven others.

Futaba Yoshioka wants to "reset" her life. In junior high, girls ostracized Yoshioka because too many junior high boys liked her.

Taken from AniDB - Once, there was a group of close childhood friends. However, by the time they entered high school, they had grown apart from each other.

Right after starting middle school, Akari Akaza joins the Amusement Club which is composed solely by her two childhood friends, Kyouko Toshinou and Yui Funami. Chinatsu Yoshikawa, Akaza's classmate, becomes a member after finding out about the dissolution of the Tea Club.

Haruhi Fujioka is searching for nothing more than a quiet place to study in the most elite high school academy in all of Japan when she stumbles across the mysterious third music room. Inside she encounters six beautiful men, the members of the host club.