Eiji has the biggest heart in the series despite him being a little bit perverted. I feel sorry for him, it's like life never been in his side. He just want someone that genuinely loves him.
NTR and this is a bit different, when you read NTR, you know that it's a hentai. You know either the wife/gf raped or cheating gonna happen.
You don't really feel that bad because you know what gonna happen and you know that its that kind of manga, you rarely get attached to hentai characters...
I'm 100% sure the shop waiter see all of those action, and goes "Holy shit, nowadays high schooler is crazy"
I mean, everytime I buy a shoes, the shop waiter wont leave me alone, so they must be see that.
What's with these comments, I think this is one of the best show of side character in this manga, it's just one of those lesson and experience in life for Gonda, it could build him to be a better husband once he got married.