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His name is Kazuki Shikimori, 17 years old. He attends Aoi Academy, a school for elite magicians. Each magician has a set limit of spells, and performing more spells than the limit allows will cause the user to turn into dust. In this case, the number of magic Kazuki can use is far below the average in his school. Then one day, all of a sudden, three girls appear before him. But of all the things that they are after, it is his GENES. And for Kazuki, the girls' appearances may also spell his doom, as he soon realizes that his magic count is decreasing ever steadily. (Source: Anime News Network)
Sequel
Kazuki Shikimori has lost his memory and has come to find out that there are three young girls after his DNA. Even though his magic is extremely limited compared to others, it is believe that his offspring will wield incredible magic. Kuriko Kazetsubaki claims to be his girlfriend. Rin Kamishiro is urged by her family to be his wife. And Yuuna Miyami claims to be Kazuki's wife, as per a promise made when they were kids.