Yuma and Hotaru have been best friends since childhood. Yuma would protect Hotaru from things such as bullies, and made it her job to look after her. Now, the two are second-year high school students, but Hotaru is anything but innocent. Yuma gets her first boyfriend and is nervous about it, so a more experienced Hotaru suggests a “dress rehearsal” to help her out. The helping out later on leads to a deep kiss with Hotaru, who says that Yuma now knows how to kiss a guy. This leaves her thinking about how much better this kiss was than the one she had shared with her boyfriend. As time goes on, Yuma worries that her boyfriend will find out what is going on between her and Hotaru. She also cannot explain these “strange” feelings she has when she is with her.