My name is Atsushi. It was only after we started dating that I found out that Muka and her sister were living together at my girlfriend's house. By the way, my girlfriend is a homely and demure girl. She's serious and passive when it comes to sex. But her sister Nozomi is terrible at cooking and housework, but very active when it comes to sex. She's a real carnivorous girl. Nozomi has a licking habit and seems to instinctively lick all kinds of things, so even though my girlfriend was right next to me, my heart and body were completely drained and I became addicted to her sucking techniques...