Muscles are denser than fat, thus if you exercise you "lose" size, but you actually gain weight/mass. This needs to be taught in basic education as a fundamental, not just the "bad foods = fat". This is why Shun has gained weight, not counting the whole "growing up and still developing" thing...
The "or did that happen" moment cements to me she's definitely the reincarnation of Mitsuki. There's been so many hints up until now, this is the last one I needed.
If cup holds liquid of a decent amount at all, it's functional. I'd like to know what author was thinking writing that part. The lip being weirdly shaped for comfort? Psh, a trifle.
To all you jokesters about body stretching, virginity, and popping out the egg, it was already proven not just in this chapter but the ones before that she doesn't actually go into labor, the eggs just appear.
Also, as to the twins, obviously the ones facing each other top left, the beast...
@HolyOrdos Rimuru used to be a male with heterosexual feelings, but one could see it as Rimuru liking girls no matter what form/sex he has. Sexuality isn't tied to gender or sex, as illogical as that sounds.