Welcome to the fascinating world of Gensokyo, in which youkai, animals and some humans live, completely separated from our world by a magical barrier. The only gateway between the two worlds is the Hakurei shrine. Reimu Hakurei is the maiden working at said shrine. Whenever problems of supernatural causes occur, Reimu goes out with her friends to investigate, eliminate the cause and hopefully restore Gensokyo to its equilibrium.

Shinya Yukimura and Ayame Himuro are two scientists that want to find out if love can be solved by a scientific theory. These two scientists also have feelings for each other and want to be able to solve their feelings through similar theoretical facts. With this perfect opportunity, these scientists will attempt to solve the theory of the love they express for each other.