He doesn't need to apologize. I'm sorry but that sounds really wrong honestly, would you apologize to your lover because you're not virgin? If Ei was uke there would be pages of arguments because this sounds a lot like slut shaming. Does this sounds alright;
"I'm sorry my dear, I had sex before we were even together so I was not virgin when we had sex for the first time. Oh I feel so dirty now! But we're equal now since I had to watch the man I love marry and have child with someone else for years."
Not for that. I think that Jin was upset because that first time was with Angelo of all people. Someone who's still around them and is openly flirty too. It's like, "hey, I fucked our friend when we were younger, but don't worry, I only did it because I couldn't do it with you" (?) I wouldn't be happy either. And btw I did say that Jin has a lot to apologize too. Not because of the marriage (Ei doesn't really need to apologize either, but if one does, the other should do it too) but for the fact that he hurt that person by doing that. Trust is something you obtain little by little, and saying sorry when something upsets our partner is a good way to help it grow. Anyway, that's just my opinion. In the "main" story Kei doesn't really apologize at all, like, ever, and I still like it lol it's just that being this one more mature and their love more consistent I hoped for more.
Yup, this mangakas semes are socially inept in general.
Honestly, I wanted an apology. Jin always felt bad about his wedding AND he gave his first time to Ei (the night before marrying lol). Both had something to apologize for. But well, I love all this series so I'll forgive that. I want to see them married and Kei & Shingo too, of course.
I still hate Angelo btw. He's a flirty bastard who apparently enjoy meddling in other people's relationships, such an attention w**re. I mean, he accused his boyfriend to cheat but he acts like that ???? Forget it.
And I almost forgot! Where's Shingo's ring???? It was said that he couldn't remove it once he wore it. That small detail made me nervous all of a sudden. If there'll be a continuation I want a happy one!!
Great job to the scanlation group. It was amazing.