I'm not a huge fan of chubby girls, not like it's my thing. But I have nothing against them either, and they're very rare in manga, and the few you do see usually all have the same archetype--they're sweet and have a heart of gold but they're self-effacing and gloomy and can't believe the guy falls for them and stuff.
Nothing wrong with those, but it means this is interesting. This girl is overweight but cute, and although she has self-doubt she gives it that try to present herself as cute, act as if she's confident. She is not really any of the typical manga-heroine archetypes, but at the same time she's still sympathetic, a good sweet kid in the end. So it makes for a more original read than typical manga romcom. Or at least, a less unoriginal read. Overall, I like it.
And I think all the people arguing about whether fat fetish is their thing, like whether something is your personal turn-on should decide whether a character like that is allowed to be presented, are missing the point.