I think his bladder is really tiny and very weak due to drinking water not really being a requirement as frequent as it is for humans. like back when he was with niwa and co as kabukimono I think he didn't have a lot of trouble with it other than just his bladder being small, he behaved human just like them which includes drinking even if it wasn't necessary. though I do think he produces more urine than the average person due to a lot of the fluid not being used. unfortunate for his small bladder.

once he denounced humanity he stopped consuming outside of the bare minimum. I imagine he's like a snake in eating and drinking habits. he only drinks to replace lost blood and not have his skin dry out.

nowadays hes re-assimilating to human society. this means taking part is social events again, and I think he studies with layla and much later, collei. wanderer just goes along with them when they bring something to their hangouts and study sessions

he does drink a lot of tea, right? after somewhat mending his relationship with humanity id think he doesn't hold back on drinking it anymore. unfortunately his bladder is several hundred years out of practice and he vehemently denies ever having to pee until he's actively leaking

i think he tries to keep the squirming to a minimum but he really can't help it. if he's asked if he needs the bathroom he would deny it and stop squirming for a little while until it'd start up again. he'll rub his thighs together, fiddle with his accessories, cross and uncross his legs if he's sitting. if he thinks nobody is looking and he's really desperate, he'll grab at himself

i think dottore should experiment on scaras bladder. fill him up to see if diuretics have an effect, if physical or psychological stimuli have an effect on holding time, and just to see scaras reaction to the utter humiliation of it all

the first time he tried it he probably fed scara way too much water, anticipating that he would have a large excess water storage lest something terrible were to happen at a diplomatic meeting. unfortunately not the case. not to mention if he has no need for the liquids it simply goes straight to his bladder. dottore dismissed scara immediately after and just asked him when he felt the effects and to not go to the bathroom or it'll lose its 'potency'. he promptly pissed himself 45 minutes later because he figured asking less than an hour later would be pathetic, and he could wait (he could not)

context, kabukimono and wanderer share kabus body through weird irminsul shenanigans and live with niwa in tatarasuna. that's all.