My Girlfriend Cheated on Me With a Senior, so I’m Cheating on Her With His Girlfriend

My Girlfriend Cheated on Me With a Senior, so I’m Cheating on Her With His Girlfriend, Kanojo ga Senpai ni NTR-reta no de, Senpai no Kanojo wo NTR-masu Kanojo NTR 彼女が先輩にＮＴＲれたので、先輩の彼女をＮＴＲます novel:

Yuu Isshiki, a first year university student, learns that his girlfriend Karen is having an affair with his senior, Kamokura. He was so shocked and devastated that he asks Kamokura’s girlfriend and the most beautiful girl on the campus, Touko: “Please have an affair with me!” A thrilling romantic comedy that begins with an accomplice relationship!