Hapiel

On her way from school, Saya was hit by truck. After recovering, she could see a bizarre being. Only she could see this being. It's name was Hapiel. Hapiel does what she wants in Saya's school, harassing Saya; she's a terrible thing! She introduces herself as an angel, and said she wants to protect Saya's life. Saya's absurd existence begins.

(Source: Kodansha, translated)