This part of your keyword is highly unusual. In anime terminology, "EP12 of 4" makes no sense. A show cannot have Episode 12 of 4. It’s likely:
Alternatively, "4 updated" could refer to chapter 4 of the manga being updated with new pages or a revised edition. Some doujin artists release "updated" versions of older chapters. But again, that would be chapter 4, not episode 12. boku ni sexfriend ga dekita riyuu ep12 of 4 updated
Note: This is likely the "updated" episode you are looking for. This part of your keyword is highly unusual
The Plot: In the final episode, the dynamic between the protagonist, Kana, and Reina reaches its peak. The narrative focuses on the stability of their unconventional relationship. Alternatively, "4 updated" could refer to chapter 4
Key Visuals & Themes: The final episode maintains the high production quality the series is known for, focusing heavily on the contrasting personalities of Kana (often portrayed as the more innocent/energetic one) and Reina (the more mature/assertive one).
The "Boku ni ga" style did not emerge from shōnen battle romances or fluffy shōjo comedies. Its roots are in seinen and josei literary manga—works aimed at adults who have outgrown the idea of "destined lovers."
"Boku no Sexfriend ga Dekita Riyuu" (The Reason I Got a Sex Friend) is a Japanese adult manga (doujinshi) created by the artist Yuzuha. It gained notoriety for its realistic (though dramatized) take on casual relationships, jealousy, and emotional entanglement.