https://www.dlsite.com/maniax/work/=/product_id/RJ01007489.html

(同人誌) [ゴールデンバニア (高橋バニア)] カップルさん大募集!!イケメン男優のテク我慢選手権

Base +9, Coledas Ukgent +13

Just guessing, seems like they are a good couple, but the guy is incredinly timid/shy, he just can't start or continue anything.
So somehow they got to hard therapy, make someone else fuck his girlfriend so he would react, or at least by passing that kind of bar, enable him to do normal stuff.
But even after getting cucked for good he is unable to KISS, a born cuck, his penis works and is not small, he is just mentally broken.

Base +10