Hotaru Mizushina

She is Yuma's childhood friend, who plays sexual "pranks" on Yuma. When Hotaru was young she was timid and shy, and was bullied a lot. She also gives Yuma relationship advice and claims that she wants to be Yuma's first.

[Spoiler] Hotaru dates Fujiwara, but it can be assumed that Hotaru is actually in love with Yuma. [/Spoiler]