Aku no Hana

Synopsis

Takao Kasuga is a lonely boy who spends his days immersed in books to escape his frustration with life. His only source of joy is the beautiful Saeki, who he secretly admires from afar. However, Takao's obsession goes too far one day when, in a moment of emotional folly, he steals the girl's gym clothes and takes them home with him. Worse, his terrible deed is spotted by Sawa Nakamura, a mysterious outcast who sits behind him in class who threatens to reveal the boy's secret unless he promises to engage in a contract with her. At first it seems Sawa just wants some companionship, but soon it becomes clear that this "contract" involves more than mere afternoon chats. In fact, Takao is about to discover just how dangerous his bond with Sawa is and how it threatens to tear everything - his life, his love, and even his sanity - apart. Source: (anime-planet)