18+ Maken-Ki!

Ooyama Takeru, a young normal yet perverted minded guy, got accepted and now goes to a school that, unknown to him, was where combat and magic is used. On the first day, he meets again after three years: Amaya Haruko, his childhood friend, Kushiya Inaho, a girl who says she's his fiancée, and Himegami Kodama, a blonde who wants to kill him. Finding out that there are many girls there that just don't like him, he is told that everyone there uses a special magic ability while using an item or weapon called a Maken. Later, he finds that no Maken is acceptable for him and doesn't know what to do, since in this school the students get into duels that showcase their magic and combat power, to which he seemingly has none.

Included one-shots:
Volume 15: Kanojo wa Muma de Irregular (She Is an Irregular Succubus)
Volume 16: Gakuen Dragon Slayer (Highschool Dragon Slayer) [Story: Yamaguchi Mikoto]
Volume 20: Ezaki-senpai, Komarimasu