I dont really find the age gap off putting or anything since as you said it's only 4 years but the thing is it's focusing quite a lot on their little romance. The age gap isnt the problem (for me at least) it's the fact that she's 10 and so so innocent like she doesn't even know why sharing that cookie with Belle in that one chapter in that way is romantic. I personally think it would be better if they started more as friends first instead of this relationship where Mabel doesn't even know that it could be in anyway more than friends but Belle does know and is thinking of it? does that even make sense lol. Ya anyways most ppl dont have a problem with the age gap just how early the romance is and the ages themselves. But I dont mind too too much since its not like it completely ruins the story or smth. ヾ(❀╹◡╹)ノ~

wait what the- why is everyone complaining abt their age gap? they still don't have any of those romance feelings yet bruh, so stop complaining. they only smile at each other tf, yeah I can see that he like her, I like him too