[Ryusei]

From withlove.info:

According to Narinari.com,
Nishino will be in charge of creating the theme song this time, and she’s excited. [She stated] the theme song is about the inner feelings of a man who doesn’t quite understand women. The song compares a girl’s mind to an instruction manual. I think that you understand feelings of a women and the message, ‘love for a favorite person’, which seems selfish yet it is not something that can easily be said or expressed straight forwardly. [Both] men and women’s feelings within the movie, “Heroine Shikkaku”, are quite complicated…