Yeah after thinking about it I really don't have a problem with this chapter. Asshole dude hits on his girlfriend in front of him and hands her his number. Natori 100% knows in his mind she doesn't mean it to come off like it does, but it still bothers him - so he talks to her about it. Was he totally levelheaded while doing so? No, but it was far better to explain why it bothered him than letting it fester. Asako understood *why* it bothered him and agreed it would've bothered her too, and they both apologized to each other.
He clearly regrets how he handled it, too. He wasn't even going to bring it up until she asked why he seemed down, even though he was trying to hide it.
It's not as if they're some perfect couple, she's super insecure and his past relationships have been pretty bad, so it's totally understandable they'd run into issues like this