It is about a girl called Hotaru Takegawa and someone called Gin (who cannot be touched by a human otherwise he'll disappear). They meet each other every summer. Their relationship was growing, they became closer to each other and fall in love. He tells her, one day, that he is neither spirit nor human. One day Gin invites Hotaru to a festival which the spirits hold and during that festival Gin touches a human boy (by accident not knowing he was human) and disappears. Just before he disappears Hotaru hugs him.
It is a sad story but it was romantic.
I wish he didn't disappear but it was a great story.
I loved it.