Sono Otoko Wagamama nitsuki

On her 17th birthday, high school senior Shiina tries to sneak into an ultra-hip club with her friends. There they meet Makoto, the very hot owner of the club. When she tells him her name, he seems surprised. However, upon learning her age, he kicks her out. At school the next day, Shiina finds out that her geeky science teacher is actually Makoto in disguise! (Source: M-U)