"You can use your swarming racial trait to enter the square of any willing ally that is the same size as you or up to one size category larger, granting you the benefits of the swarming racial trait as if your ally were also a ratfolk with the swarming racial trait. "
So it says you can enter an ally's square. But I'm not seeing anything that would let an ally enter your square. Is this correct that an ally can't be the one moving into your square?