10-nen Buri ni Saikai Shita Kusogaki wa Seijun Bishoujo JK ni Seichoushita Ita

Isamu Arizuki (28) 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.......?

(Source: Overlap, translated)