Hensuki: Are You Willing to Fall in Love With a Pervert, As Long As She's a Cutie? S01 E01 Cinderella Dropped Her Panties?!

Keiki Kiryu is a kind-hearted high school student surrounded by attractive girls. One day, he finds a love letter with no sender information, other than a pair of panties. Keiki begins his investigation by speaking to his senpai, Sayuki.