Yami ni Oboreta Tenshi ni Kiss wo.

"This is a secret."
Mio Shirano, an ordinary high school girl who enjoys reading, gets closer to her classmate Takuya Kanda when he asks her to tell him about a book she recommends. Kanda has a handsome face that makes him look like a picture when he reads, and his school uniform is well-dressed and neat. Mio is happy to be able to talk with Kanda, whom she admires, but she discovers his secret in the infirmary. And that was the beginning of an inescapable love affair with Kanda.