19 short stories by 19 different writers.

The protagonist, Awaya Yukiguni met a girl named Isuruga Mitsu and fell in love with her at first glance. Later, he learned that Mitsu is commuting in an all girls school, the same school that his sister attends. So in order to approach and become closer to her, Yukiguni decided to attend the all-girls school in place of his twin sister.