also known in the short form is a Japanese harem, romantic comedy light novel series written by Tomo Hanama and illustrated by sune. It was published by Media Factory under their MF Bunko J imprint from January 2017 to January 2022. A total of fourteen volumes have been published. The series follows Keiki Kiryū, a high school student who seeks the identity of the sender of an unnamed love letter attached to underwear, which consequently leads him to discover the special hidden peculiarities of the girls in his life.
