Rotten

Rotten (腐, Kusa) is chapter 16 of the Boku wa Tomodachi ga Sukunai light novel series. It is chapter four of volume two.

Summary
On the day after a new member joined the Neighbor's Club, Rika asked what activities the club holds as her fellow club-mates do their usual thing.

Kodaka: " Well, we don't really have any specific stuff we do right now. Whenever someone comes up with a good idea for making friends we usually just go with that and see what happens. "

Rika: " Well then Senpai, why don't you try having intercourse with Rika? "

Kodaka, Yozora, and Sena immediately snarked at Rika's casual remark, and Rika preached to Yozora about the existence of sex friends (friends-with-benefits), and about how males and females wouldn't normally just maintain in a friend zone, causing Yozora to retort back at Rika.

After teasing Kodaka on acquiring his genes, Rika showed the others her doujinshi. After reading it, the others find it surprisingly interesting, finding it hard to believe that a doujinshi such as theirs was done so professionally. Rika and Sena then converse about the coupling between manga/anime character, which Yozora is unfamiliar with, but was surprised after learning the fact about it from Rika (which she explained in an absurd way), and causing her to fling insults towards Sena knowing she is familiar with the "coupling" Rika was talking about.

Rika then approved of her perverseness towards others, causing Kodaka to retort back at her, claiming Rika as a fujoshi (or a nasty old geezer). After tackling about a "Rika x Kodaka doujinshi", much to the latter's annoyance, Rika was getting turned on from watching her senpai (Sena) re-read her "porn" repeatedly, causing Sena to get puzzled over her doujinshi, which she states that she didn't read any lewd things since there aren't any human beings in it, which turned out to be that Rika's doujinshi are Mecha x Mecha, causing Sena's to get confused as she continues to flip through the pages in Rika's doujinshi, as well as Kodaka, who was reading a scene in which the two robots are "fighting".

After reading, Sena was utterly confused about what she read, while Rika remarked on how enjoyable it was even if she reads it repeatedly, causing Yozora to call her insane. Though Rika claimed that she was well aware of her "insanity" and that nobody will ever understand her, but nonetheless, she stated that she will never lose and that she will get strong all the while shouldering the burden of being a pervert, which she was born with, much to Kodaka's disgust.