Common ground like the numerous things they have in common or the mutual respect they have for each other?
The only big differences between them are how reserved Rihito is, how impulsive Noa is, and how sociable they are. Otherwise they do very much get along, as we’ve seen for 23 chapters now.
A lot of readers make the mistake of self-inserting themselves as Rihito and therefore imagining Noa as annoying or hard to deal with, but they’re fictional characters and the story is clearly depicting them as good friends - even if their energy levels don’t align. Rihito has already explicitly told Noa that he doesn’t think she’s annoying, he just prefers time to himself.
Also, at a certain point it doesn’t matter how possible this friendship would be in real life. This is fiction. Just like we accept it as normal that Goku can shoot lasers from his hands, it’s best to just accept their relationship as is. Certain things just probably won’t be explored because this is a specific type of slice of life friendship/romance comedy. Not a drama or character exploration. Suspension of disbelief and all that.
My issue isn't the conflict between their personalities and energy levels (I think it's part of the charm), it's some of the absolutely toxic behaviors Noa exhibits that are being played for laughs. She doesn't respect boundaries, she's manipulative, and she's controlling just to name a few.
And I will say in her defense that she doesn't appear to be consciously aware that she's doing the last two, but they're tied into her unaddressed issues with low self-esteem.
I had a very similar friend/coworker once. We had a lot of stuff in common, got along really well, had a great time sharing hobbies, etc. And just like Noa she had a lot of issues with her self-esteem, which lead to a very similar set of toxic behaviors. Constantly reminding me that I was her "only" friend, getting upset if I didn't respond positively to her, demanding to be informed about my schedule so she'd know when I wasn't going to be at work, getting upset when I couldn't chat because I had projects to take care of, etc. Eventually I had to go see a therapist because it was stressing me out so badly, and that ultimately ended in me having to completely sever from her.
Now this is a romcom, so I'm sure things will turn out alright in the end. Rihito and Noa will somehow make it all work out, and there will be hijinks aplenty. But there's still a part of me that wishes the toxic behaviors were addressed or at least toned down.
