Otome Dori (2012)

Although they aren't dating now, Okino Kazuki is confident that he’ll end up with his best friend Sakuragi Otome. They live happy lives, oblivious to the jealous looks they get from the other important person in Okino’s life, his sister Rinka. Their blissful innocence is brought to a halt when Okino sees Sakuragi led away by a perverted older man. After that, Okino begins to receive the DVDs. They contain porn starring the love of his life, and as Okino watches them one by one, he notices a change in Sakuragi. As Okino questions whether he can love Sakuragi as she is now, he learns that there are other things he should be worrying about. How did Sakuragi wind up with the men in the videos in the first place?