My girlfriend's sister loves me so much that we secretly make babies

Storyline: Matsumoto Ichika, who is really full of little sister vibes, makes her first appearance in Honnaka's popular series! "Hmm, your boyfriend couldn't have sex with your sister. Poor thing, shall I do it for you?" She approaches you at close range and boldly seduces you! "I don't mind doing it raw if it's your boyfriend" You can't hold back when she stares at you! When she's not around, you end up in a relationship where you cum inside her many times.