We don’t really feel that Hoseok has boundaries when it comes to personal space and he would likely be drawn to a girl who is likewise unembarassed about being around each other most of the time, even during less - uhm - glamourous situations such as using the bathroom. He would find himself just walking in to use the toilet if you had not locked the door and would think nothing or talking to you through the shower curtain/cubicle. He would be the most likely to spend a while in the bathroom with you, either doing his ‘business’ or just procrastinating on tasks he is supposed to be doing by talking to you. (See our Most likely to be distracted by you when working post). If he could not hear you properly over the loud sound of the running water, he would have no objections to pulling back the shower curtain or opening the cubicle to understand you better. There would never be anything seedy here though. While Hoseok might look at you naked while in the shower, he would not think anything overly sexual of it. We feel that Hoseok would be very comfortable with you early on in the relationship and would not feel he had anything to hide from you and vice versa. He would be a little put out if you told him you minded him using the bathroom while you were in there as he would not see it as anything taboo but he would eventually understand and leave you to your privacy.
While we don’t feel Jin would do anything more than pee when you were in the shower, we feel he would rather use the bathroom you were in rather than go to another in the house as he would love those few moments of being in close proximity to you and being able to chat to you through the curtain/cubicle. He would knock on the door and call that he needed to pee before coming in. He would often make little jokes and end up making you laugh. His windshield laugh would echo through the room, making the situation even funnier. He would never deliberately look at you or pull back the shower curtain though as he would respect those personal boundaries. If you asked him not to come in when you were showering, he would be dissapointed but would respect your wishes and stop doing it.
We feel like Taehyung would not object to using the bathroom to pee if he needed to, but would make it brief. He would give a little knock before coming in but would not really make much conversation. He might find his eyes flickering to the cubicle, unable to help himself, but would leave shortly after, not bothering you any further until you were out of the bathroom.
While he would try to wait until you were out of the shower, if he needed to go, Yoongi would not be embarassed about peeing with you in the shower. He would give a little knock before walking in to warn you. He would not be against making small talk while he was using the toilet, but would not be overly chatty like Jin and Hoseok. He would not deliberately avoid looking in your direction but also would not be overly turned on by seeing you naked. He gets his pleasure more out of being close to you and is generally very mature when it comes to sexual things.
Although Namjoon would use the bathroom if he absolutely had to, we feel he prefers having his own space and would feel embarassed about having to walk in. He would try to be as quick as possible and make as little conversation as he could before leaving. He would try to avoid looking at the cubicle as much as possible but would probably end up flicking his eyes towards that area of the room due to feeling so seedy anyway. He would feel guilty afterwards, even if he only caught a climpse, and would curse his lack of self control.
We feel like Jungkook is inherently bladder shy and would be physically unable to use the bathroom while you were in there. He would be embarassed about this, especially if you told him he could use the bathroom - he would just stand there, unable to pee. If he was absolutely desperate, he would end up having to resort to embarassing measures such as urinating in a plant pot or an empty bottle, as he would just be unable to use the toilet in your presence. You would ask him afterwards why he did not just go next door and ask the neighbour. He would feel even more humiliated as he would not have thought of that.
We feel like Jimin would not want to use the bathroom while you were in there as he values his own privacy, and would find it a bit ‘dirty’. If he was absolutely desperate and there was no other bathroom in the house, he would go next door to use the neighbours bathroom.