Alright, lets break it down.

>"The manga has kiddy tits and characters visibly soiling themselves."

Because, just like in the real world, not every culture treats nudity as this abhorrently bad thing we need to shy away from, for many something like that’s just natural, hell, it’s already natural for boys, but people like you only make a fuss over it when it happens to girls because your culture and upbringing taught you it’s “wrong and inappropriate”. Said scenes of toplessness/nudity aren’t done in an exploitative way, characters don’t suddenly get nude/topless “just cause”, they do so when it’s natural to do so, and the manga chooses to show it because it's just natural to them in that setting, so who cares? That's why many of the characters are so casual about it, the way the world works is more straight forward and doesn't tip toe around a lot of usually adult behaviors, themes, and habits, I mean they train kids to go into a murderhole to look for artifacts, and the general reaction to things like dead bodies, the effects of the abyss, and so on are "meh, just part of the job”. That theme of not tip-toeing and showing thing in all its grit carries over into many things, including the peeing bits. Those aren't done so some degenerate can get his jollies off, it's meant to either show the character preforming a natural function, or convey a sense of real and gritty fear/pain.

1/2

Cuddle the bun
Do it hun