Noya Itsuki just started his school year at the Ebisugawa High School and since he has always had a fascination with space, he decides to join the astronomy club. However, he mistakenly walks into the all girls Otaku Club. He notices that the members are really weird, but Itsuki has yet to realize that he isn’t in the astronomy club. His life is about to get complicated by being surrounded by so many girls..

An unfortunate high school student, Ayasaki Hayate spends his days working at part-time jobs to support his extravagant parents. After incurring a debt of 150 million yen, they disappear, and Hayate was left holding the bag. Whilst running away from the debt collectors, he tries to kidnap a girl for ransom (however, the girl misunderstands his intentions and thinks he is confessing his love to her). Almost immediately, he botches the kidnap attempt but then manages to save her from other kidnappers, causing her to fall in love with him. The girl, Sanzenin Nagi, is actually the daughter of a millionaire family. In recognition of his services, she hires Hayate as a resident butler and even pays off the debt collectors. This is how Hayate becomes a combat butler. In order to serve and protect his mistress, Hayate's life-or-death butler life begins. (Source: AnimeNfo)

The members of the student council of Hekiyou Academy are chosen by a popularity vote. As a result, all the members are cute girls except for Sugizaki Ken, who studied hard to enter the council. This novel is about the endless chatters of the members, full of parodies from various other works such as "The Melancholy of Haruhi Suzumiya", "Dragon Ball" etc. The series was originally planned to be titled as "Hekiyou Academy Student Council's Minutes (碧陽学園生徒会議事録, Hekiyou Gakuen Seitokai Gijiroku), but because of the length, the title of the first volume "Seitokai no Ichizon" was chosen to refer to the whole series. It is also called "Seitokai Series" by some.

H2O's story revolves around Takuma Hirose, a blind young male junior-high school student, though the cause for his blindness is undetermined. After his mother died an unexpected death, it left a deep emotional scar on him, which caused him to become very lonely and reserved. Due to this, Takuma and his father move from the city out into a rural area and Takuma is enrolled into a new junior-high school. At his new school, he meets several new girls, though three of whom he gets to know the most out of anyone else. They are, the firm and obstinate Hayami Kohinata, the kind and obliging Hinata Kagura, and the cheerful and mysterious Otoha.

Spin-off series for the Seitokai light novel series.