ビッチになっていた俺の幼馴染について ～俺と真凛とセックスフレンド～

あらすじ

The protagonist and Sakurai Marin go way back - they've been thick as thieves since childhood, and even now, they often bond over gaming sessions. Though their close relationship sometimes raises eyebrows, he brushes it off as nothing more than a lifelong friendship. Given Marin's vibrant social life, it wouldn't be surprising if she already had a boyfriend, believing it wouldn't affect him in the slightest.

One day, after playing games and chatting with Marin, he glances at his screen later on and realizes she forgot to turn off the camera. To his shock, he spots his childhood friend in her room with an unknown man, giving him a titjob. She's surprisingly unfazed when she later discovers he witnessed the steamy scene. She drops another bombshell: the guy, Shitaka Eiki, isn't her boyfriend but a friend with benefits.

The protagonist is shocked not only to learn that Marin is having sex with someone else but also that she has several other fuck buddies. He urges her to quit fooling around, but Marin calls his bluff, suggesting he's just itching to get laid himself. In a bold move, she gives him a blowjob and takes his virginity while he's unable to resist.

From that moment on, the protagonist can't shake Marin from his thoughts, and he grapples with conflicting emotions about her promiscuous lifestyle. He makes another attempt to persuade her to ditch her numerous sexual partners, but she accuses him of wanting to monopolize her body. She proposes he joins her roster of sex friends if he's that keen to jump her bones, but he adamantly declines, insisting that's not what their bond is meant to be.

Afterwards, the protagonist continues agonizing over his relationship with Marin while she begins to flaunt her intimate encounters with her sex friends at every turn as if deliberately provoking him.