If Your Sister Puts a Swimsuit on...
Nao coerces Shūsuke into going to the beach with her, though coincidentally they end up running into Haruka, Hirono and Iroha, who Nao recognizes as the pigtailed girl from Shūsuke's childhood photos. Nao and Iroha end up competing with each other for Shūsuke's attention, though it tends to just bring him pain. Nao accidentally knocks him unconscious with a rented boat, and he dreams of his favorite eroge character. Nao and Iroha compete with each other over who gets to perform mouth to mouth resuscitation, though in the end, he is revived by one of his male friends.
Aired 30/01/2011EP 4 - If Your Sister Puts a Swimsuit on...

I don't like my big brother at all!!
Junior High student Nao's brother complex is so strong, it's almost at the point of incest. She's determined to make her brother, High School student Shuusuke, see her as a woman. So determined, that she goes as far as going into his room to throw away all his non-incest related porn. But as she's looking for his porno stash, she finds a photo album... and she's not in any of his childhood pictures. What is going on?