Onii-chan, Fuck Me First

 "Onii-chan, Fuck Me First" ( Oni-chan, Watashi to Shiyō yo お兄ちゃん、わたしとしようよっ)     is the first episode of the Imouto Paradise! OVA. It was released on December 9, 2011, by MediaBank, under their GOLD BEAR label, and directed by Murakami Teruaki.

Full Summary
Sōichirō is woken up by Aya, after having a very erotic dream of her and Rio. Hiyori asks him what masturbation is, which leads to an awkward conversation at the breakfast table. Sōichirō accidentally catches Aya masturbating in her room, whilst she is fantasizing about having sex with him. Soon after, Aya realizes that Sōichirō saw everything. Later, Koharu walks in to Sōichirō's room when he is watching porn, that leads to them both having sex. Aya admits to Sōichirō, that even though she's his sister, she thought about him while masturbating, and apologizes before confessing her love, which leads to the two having sex. Whilst the two are laying down together, Sōichirō says that he loves her, and that they are all his precious sisters, which makes Aya question the word sisters in her head.

 When Hiyori wets herself, she asks Sōichirō if he is going to punish her. He first says no, but then considers this and tries it. Koharu later asks him if he wants to play with her again, and he denies this, saying "the devil made me do it". Aya overhears this, and wonders if he did it with Hiyori and Koharu too, before coming to terms with the fact that he loves all the sisters. Later that day, Rio agrees to let Sōichirō see her breasts, and they end up having sexual intercourse, Rio reluctant at first. The episode ends revealing that Aya was outside the door.