Koisuru Tenshi wa Tsumibukai

In a world where angels walk among humans, friendless high school girl Misora Shiratori has one goal: to receive the gift bestowed upon only the most outstanding angels—a divine halo. That's why she lives her life with the utmost sincerity and why, together with her beautiful classmate Kanade Agoshi, she decides to join the student council! But her world is turned upside down when she finds it not to be a haven of virtue, but a den of desires so deep and twisted that its seven members are known as the Council of Deadly Sins...

(Source: Yen Press)