Soen ni Natteita Osananajimi (Kareshi Ari) wo Sex Friend ni Shitemita (Shinjou Shimai Hen)

"That's messed up. Doesn't that make you just a sex friend?"

Futaba Shinjo, a fiery, competitive member of the swim team, scolded Aya Kurasugi, her respected senpai. But I'm going to punish Futaba for spying on Aya and I, by taking her virginity and making her my sex friend, too. I erased Futaba's relationship with her adoring childhood friend by forcing her to call him up only to hear her climax live on the phone. And then I turned my eyes on her kind-hearted older sister, Kazuha, who goes to an all-girl's school…

(Source: France Shoin, translated)