10-Nen Buri ni Saikai shita Kusogaki wa Seijun Bishoujo JK ni Seichou shiteita10年ぶりに再会したクソガキは清純美少女JKに成長していた; The Brat I Hadn't Seen in 10 Years Turned into a Pure, Beautiful High School Girl.; Kusogaki Who Met Again for the First Time in 10 Years has Grown into an Innocent Beautiful Girl JK.; La mocosa que no había visto en 10 años se convirtió en una pura y hermosa chica de secundaria

Yuu Arizuki returned to his hometown after quitting his job at an black company in Tokyo. Just as he was getting ready to start a new life back home, he met a beautiful and innocent JK girl, who turned out to be Haruyama Miya, one of the little girls (brats) Isamu used to play with when he was young. But Isamu didn't recognize her because of how much she had changed after growing up...?