InCha Couple ga You Gal-tachi to SEX Training Suru Hanashi

An inexperienced, gloomy couple is being developed by a group of extroverted, bitchy gals...! The fate of Akiho, the boyfriend who has never had sex yet, and Suzune, his girlfriend, changes dramatically when they accidentally meet their childhood friend Sayu, who has become a full-fledged gal. The two have their first experience at the hands of the gals, and discover the melting pot of pleasure. When Suzune sees her boyfriend being taken advantage of by the three gals, she makes up her mind and pushes Akiho down...!?

(Source: lune-soft, translated)