https://www.dmm.co.jp/dc/doujin/-/detail/=/cid=d_405988/
https://www.dlsite.com/maniax/work/=/product_id/RJ01215967.html

I lwt my girlfriend who I couldn't satisfy sleep with someone else

"My college life with my beloved girlfriend was going well... except for one thing..."

The protagonist, Takashino Yoichi, has a girlfriend named Karai Yumi whom he has been dating since high school. They attend the same university and are happy, but there is one thing that bothers him.
That is, he always finishes first and is not able to satisfy her. He gradually begins to think about what it would be like if it was another man, and he confesses his sexual preferences to her.
The two set a condition and try to cuckold her, but after sending her off, Takashino becomes anxious.

Base +19, Coledas Ukgent +15, SadMookz +4

https://www.pixiv.net/artworks/119866545

The artist is 骨式(honeshiki).

Base +30, Zaghurim +9

大奶妮可女友被NTR

Base +2