Haite Kudasai, Takamine-san Episode 12

Takane Takamine is the goddess of her high school. With perfect grades, athletic prowess, and unrivaled beauty, this student council president is the apple of everyone's eye-including Koushi Shirota, a below-average student with no friends or social prospects whatsoever. But he'll soon find out the secret behind Takamine's unbelievable success-her underwear! When she strips, she can undo any of her past actions, and now that Koushi knows, Takamine won't let him off so easy...

(Source: Yen Press)