Sei-chan Capacity Over desu!

Synopsis

Futaba Ito is just about to start her first year of high school when Seiichirou "Sei" Izumi, her childhood friend, decides to move into the Ito residence because of his overseas-based parents. Sei is quite the charming young man and two years older than Futaba—the same age as her elder brother, Tsumugi. Naturally, Tsumugi is wary of leaving Sei and his sister to their own devices, and he has a quick chat with Sei to assert that he won't tolerate any shameful behavior. Sei agrees―but teenage zeal is a difficult thing to control.

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