Hana Ni Kamiguse summary:

Even in her second year of high school, she has no friends. A young lady, Suu, who is a "loner" to the extreme, dreamed of a normal, uneventful adolescence. Then one day, a beautiful young man named Yuki appears in front of her. He was a mysterious boy who had lost his memory and was the first friend she had ever made. But what is he really...?An instinctive love affair with a dangerous and sweet beast.