Koisuru Tenshi wa Tsumibukai

Set in a world of angels with various kinds of wings. Misora, a young girl who attends a preparatory school, tries to be a good girl every day in order to win the "Angel's Halo," a prize given to the best students. One day, she is appointed as an elected member of the student council. At first she is happy to hear the news, but it is run by students who embody the "seven deadly sins," such as wrath and gluttony. Misora is assigned to the duties of the student council together with the most beautiful boy in her class, Agoshi, who is also appointed as member of the student council, however... (Source: Natalie, translated)