Now keep in mind that i'm impartial here. If i'm in error, then so be it. Not here to flame or any other BS like that.
First off, this barrier. From what Nathan tells me, as well as the profile wiki entry, it will differentiate friend and foe alike(how it does or not is not in question. It simply does...). Simple as that. The whole business about it singling out Rakudo would be quite logical considering at the time of his post, he did not post anyone entering with him, and therefore would be on watch/detected by himself, which Yujo could take advantage of, giving him a reason to spot Rakudo and focus on him.
Second: The epic hearing. With the above point being stated, Yujo would focus on him due to being linked to the konoha barrier. Now according to Yujo, he was trained in the Ototon hearing which lets him hear over a village apparently. Trained for 6 RL months to get a correct duration of time. With that training duration, I'm assuming that one would be used to the overwhelming amount of voices, noises, etc and therefore would have lived past the disadvantage of having superman hearing, eliminating the fact that he would oh so suddenly be assaulted by every noise in the world. While, yes, it's rather outlandish to have such a range on anything, one cannot dispute training, else Rakudo would lose his "fastest man alive" title, Kirk would lose his character(or most of it anyway) etc...
Third: The kamui. From what I've picked up on the jutsu from the years on SL, kamui has always been considered instantaneous. The creation of the barrier is, at least. I might also mention that the escaping of the barrier, once concocted is impossible through most means. The closing of the space time barrier would be the part that takes time to use depending on the level of ability that the user boasts with the technique. Yujo would have that in the bag, considering he's GM of the Uchiha and his character has always had the ability, covering both the RP and in game aspects of the situation. Simply running out of the barrier would not suffice in escaping it.
If there's anything I missed, please inbox me and i'll edit the post, otherwise this is simply my input. If Yujo's post isn't legit, then a simple repost would be able to fix everything in my eyes.