Doutei Help! ~Hatsu Kano no Tame ni Fuuzoku de Tokkun~

Welcome to Soapland "Cinderella." The protagonist, greeted with those words, stiffened up nervously. His friends were all graduating from their virginity left and right, but he was still a virgin. Then, out of nowhere, he got his first girlfriend. They’d been dating for a few months now, but they still hadn’t done anything beyond holding hands. But he’d heard that modern couples break up quickly if the guy’s bad in bed… and that thought started eating at him. Around that time, he met a girl from Soapland "Cinderella" and decided to use her to hone his skills. To satisfy his girlfriend, the virgin protagonist began frequenting a soapland…! [Translated from dlsite]