Takuto Hasegawa is an Ordinary High-School Student, but his high school is of a different sort. The Magician's Academy, a place dedicated to training mages and mystical creatures of all sorts. It is insane. During a summoning exam, Takuto accidentally summons an insanely powerful familiar in Tanarot, a girl with the mind of a child and enough power to destroy a country. Luckily, Tanarot is loyal to her creator/"husband".
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