Based on the eroge visual novel Harukoi Otome ~En de Gokigenyou~ by BaseSon.

Harukoi Otome revolves around protagonist Akihito Hayasaka, a male high-school sophomore. The high school he attends St. Francesca Academy used to be an all-girls school, and still has a high percentage of female students. Akihito's younger sister (Umi Hayasaka) and his childhood friend (Yuika Serizawa) are also students there. Akihito meets many girls there, and becomes friends with them.

(Source: Visual Novel Database)