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...