Silly comments

Yeah, nothing wrong with adults sleeping around

The issue isn't that, the issue is literally the words Suzuki said right before it happened to Sugiki, the Manga is still good and they ended up together so who cares, but it doesn't mean what he did isn't shitty and doesn't make sense as to why he would do it to begin with.
The movie might not be as good as the manga but at least it removed a lot of the problematic stuff this Manga had, including something that does count as cheating even if they were never together.

It's like you are going on a few dates with someone, you two aren't official but things are getting REALLY serious, then you discover your almost boyfriend slept with someone while going out with you.
It's still shitty and wrong, even if you two aren't officially dating.

People aren't overreacting, they are saying the truth/what's right, you shouldn't do this.

They were not going out at all.Infact the relationship never started. Yeah theyre in love with each other but if no relationship ever started, it is not cheating.

And I read that, I know it.
But right before that he EXPLICITLY said "I won't sleep with other guys" so even if not dating the relationship was serious enough to NOT be doing that, he promised and what do they show us next?
Him after having slept with another guy.

The fact that he made to promise to not sleep with other men means the relationship even if not dating was serious enough to NOT sleep around/he shouldn't be doing that.
It's not like I'm pulling that out of nowhere, it's literally written there, so by definition I should take the "I won't sleep with other guys" seriously given it's literally a promise he made, not just a white lie.

Your so right queen, ngl everyone is so unserious nowadays, as something important as love, having feelings for each other even if it isn't official or have a label on it is still smthng , honestly people who back this crap as unserious must have cheated a lot or just crazy

Exactly, if someone defend this behavior there is no way they aren't fin with cheating or being with someone who's cheating on their partner, it's so disgusting how they defend this behavior just because they aren't together.
They clearly aren't nothing either if he had to make such promise.

It would be like going steadily to a date with someone, maybe you two are at you two had 20 or who knows how many dates, things are clearly serious even if not official, then you discover your date has been having sex with others while going on dates with you, that's disgusting and disrespectful, this is the same identical thing.
It's even worse because he actually promised him.

I wish that chapter would just disappear from this Manga, but it exist and they still got together as far as I've seen so it is what it is, but I expect Suzuki to tell him the truth and beg for forgiveness until the day he's a old man because he broke his trust, that's disgusting.

I swear I don't get how people can't understand that a relationship can be serious and exclusive even when not together.
It's one thing if he didn't promise and didn't feel anything to him, he didn't owe him exclusivity in that case, but he did promise, they did get to a point where their relationship was clearly on the exclusive side even if not together.