>>195816
It's a body positivity thing, but there's definitely a sexual element to it and they know about it. Inori-chan's solo song on their album basically translates to "hurry up and tell me, do you like chubby or skinny?"
If you look them up on twitter, they're in the same circles as the out-and-out bbw models, weight gain girls, that kind of stuff. Some of them follow each other.
Honestly I'm sure they're just girls who are aware that some guys are into that sort of thing, and they want to capitalize on it. Most of them were idols before they were fat and wanted to keep the idol life going. I'm okay with that!