18+ Hiota no Kanojo ga Ore no Motteru Eroge ni Kyoumi Shinshin Nanda ga......

Kazuma Odagiri, an average boy with a love for erotic dating games, is used to hiding his hobbies and being told to go out more by his childhood friend, Ruri Shinomiya. All Odagiri wants though is to find a girl that also likes eroge, but he knows that's impossible.

To his shock, one day, the school's prodigy and beauty, Honoka Misaki, finds out his secret hobby, but instead of telling it to anyone, she suddenly confesses that she wants to be his girlfriend and wants to be conquered by him! Odagiri agrees after Misaki seems okay with the fact that he's an otaku—as a matter of fact, she wants to know more about eroge and have him teach her how to be the erotic girlfriend of his dreams...!

(Source: Manga Rock, edited)