@SotiCoto At this point I'm just gonna quote myself. This was in Ch2.
I've been in this situation (manga-comment) a few times, and I have to say the same thing every time. I first noticed my classmates (plural) wearing a bra in 5th grade (11yo). And in 6th grade at least 2 of them were definitely bigger than this girl. Notice other girls here aren't quite as developed.
So personally I don't have an issue with 2/3 girls out of 15 (if we go for a 50/50 ratio) being somehow developed. What does bother me a bit is that they don't LOOK 12. Body proportions, face shape, etc. The boobs are just an extra.
Now, the chick in this chapter MAY be just about as big as my classmate was. But really, she was huge. I wouldn't call her the norm. I'm just saying, definitely possible.
But thing is, the girl in Ch2 was 12. Almus is supposed to be 10, some kid said, and Yuria said same age as Almus, so...yeah, Yuria especifically is a bit weird.
But again, NONE of the "kids" look like kids, so...yeah...