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.

Timeslip!? Kazuto is sent to the other world one night when he is sleeping back in his own world... He wakes to find himself in the Koihime Musou universe. The adventure continues in this alternate version of the classic Chinese historical novel "Romance of the Three Kingdoms". Shin Koihime † Musou has all the characters from Koihime † Musou as well as new ones that make their first appearance in this game for a total of more than 50 characters.