Hibaru Shunsuke Manga

Usami Nagisa is a yankee who suffers from a rare disease which causes her health to decline if she feels lonely. Sewa Natsuhito, the boy who sits next to her in class realizes this and keeps her company, but the only way Usami believes she can cure her illness is to make lots of friends, a process she might find harder and complex than she initially would have hoped.

Touka Aizuki has a crush on her classmate, Ryoutarou Mimori. Even if she has feelings for him though, she never acts like it, instead being cold towards him every chance she can get. But one day, she realizes that she has turned invisible! Now with no witnesses, she can show her love towards Ryoutarou. Unfortunately...Ryoutarou is the only one that can see her!