Kousaka Kyousuke discovers that his perfect little sister, who he is not overly fond of, has a secret stash of erotic games.

Kirino grills Kyousuke over why he hasn't progressed in the game she ordered him to complete, making him think she needs some friends to chat to. She joins an online community and attends an otaku event.

Kirino meets her first otaku friends, Saori Bajeena and Kuroneko, who spend their days discussing their otaku interests. Kyousuke feels at ease until he senses an alarming presence at home.

Kirino's public friends Aragaki Ayase and Kurusu Nanako come to visit and she tells Kyousuke they can't see him. A package arrives and she rashly opens it, unaware that it's from Saori Bajeena.

Returning home from an enjoyable Summerket, they bump into Kirino's best friend Aragaki Ayase, but despite the quick thinking of Kuroneko and Saori Bajeena, Kirino appears badly rattled.

Akagi asks Kyousuke about his relationship with Manami. He insists their relationship isn't romantic but that he doesn't want her to see anyone else; Kyousuke helps Manami's family put on an event.