Set in a world populated by angels who possess various kinds of wings, a young girl named Misora attends a preparatory school where she strives to be a perfect student every day. Her ultimate goal is to win the Angel's Halo, a prestigious prize awarded to the best pupils. Misora is a serious girl with few friends, and her dedication leads to her being appointed as an elected member of the student council. Initially overjoyed by the news, she soon discovers that the student council is run by students who embody the seven deadly sins, such as wrath and gluttony. To make matters more complicated, she is assigned to her student council duties alongside Agoshi, the most beautiful boy in her class, who has also been appointed as a member. Together, this serious girl must confront a group of handsome but troublesome angel boys, the so-called sinful student council, and attempt to straighten them out.