Claire, an orphan living at the Usifrim Academy, has spent her life preparing to bond her soul to a demon in order to fight for a safer world. She wasn't prepared for Nero Kelldonis, a strong and sexy demon of the seventh sin, Lust. Claire's moral foundation is shaken and her long-time crush boils over. All this, coupled with her fragile self-esteem, is wreaking havoc with her save her home from utter destruction.