High school student Kuromine Asahi is given the nickname Leaky Basket for his inability to keep secrets. He has a crush on classmate Shiragami Youko, but he discovers that she's actually a vampire.
Asahi is determined to keep Youko's secret for her sake, as her father has said that she would have to quit school if she were found out. But Youko accidentally reveals her wings while she has lunch after school.
With Shiho joining Asahi's class, things were already complicated enough. To make it even more so, a girl with horns shows up at school, and it turns out that she's actually a devil.