Board Thread:Questions and Answers/@comment-30535075-20180216171039/@comment-44061-20180326011425

There seems to be a lot of confusion here. Muken is not a separate dimension. It's simply the lowest level of the central underground prison which is itself located under the 1st Divison. There is enough space to describe it as vast and infinite and etc. To denote the characteristics and dimensions of the area as well as the bleakness as well as serious nature of the lengths of what kind of prison the worst offenders of soul society are placed into, but it is not a separate dimension, that would be simple miss interpretation on your part as in your own example it existing as a separate dimension is never stated but what is described is the amount of space. Also, literally Yhwach, Shunsui, Unohana, Zaraki all went down there and we see multiple times 3 of them have entered through a door. Its explicitly stated to be under the first dimension and underground. Shunsui even explains what would happen to the key if he died. Simply saying it the door would be sealed and there would be no access to the outside. He never alludes to a dimension.

As far as the Royal Palace it's an inner dimension which is located within Soul Society. The barriers are for protection as is the giant gate sometimes seen surrounding the seireitei. One needs the Royal Guard to enter and they need a transportation device (such as the cylinder the royal guard arrived in) to get up there and usually a form of transportation to get down (stairs or the cylinder the royal guard arrived in). Its removed for protection but not dimensionally in the way your thinking one gets to and from the human world or hueco mundo. Its the difference between trying to get to a house around the corner that's got a lot of fences, gates, walls, and security. Its hard to get in but you can walk or drive there. Whereas unless you have a spaceship it's not likely your gonna make it from NYC to the Moon. So the issue is distance. Its easier to get to and from the royal palace while in soul society and vice versa then opening up portals to and from soul society and hueco mundo. Yhwach used a portal cause he had no way up there otherwise. He wasnt invited by the Royal Guard. He had to wait for the defenses to be down in order to even facilitate entry.

To your original point. Aizen senses the last remnants of yhwachs power dissipate. Once again he is strapped to a chair, not in another dimension but just really far down and really spacious if you will. Given the level of aizen's own spiritual power, (which is muted to a small area while in the chair he is in) he is still very much capable of sensing reiatsu. Its shown countless times shinigami identifying subordinates and superiors from miles away based on sensing their reiatsu and can tell what they are doing (i.e. fighting), which direction they are or their state (i.e. dying, etc.).

As far as the royal palace first, there is no indication whether he was sensing anything. At this point, he was above ground and talking to Shunsui a bit, Who basically told him a page before what they were doing. Yea nobody told him Ichigo was up there but everyone was going to the palace, which aizen commented on, so if ichigo wasnt already there the logical train of thought is that everyone else is catching up and ichigo is already up there. Unless Aizen isn't smart enough to know that. Literally, everyone knew Ichigo and Yhwach were fighting in Royal Palace, you could likely sense that but It makes sense that it would be the case seeing as that's why Ichigo went up there in the first place. More importantly, he never said he sensed it and even if he did it wouldn't have mattered cause it was a logical deduction and he in the instance you give says "i was certain...". So by your estimation, the grand design maker Aizen literally would still operate with outdated information about Ichigo's power status from the last time he fought him. It just doesnt seem that this dimensional sensing power your advocating for is anymore then logical deductions and reiatsu sensing.