Board Thread:General Discussion/@comment-24815992-20140427193041/@comment-8986886-20140427205714

When Aizen was revealed as a traitor, and the one actually responsible for the crimes which Kisuke was sentenced for, there'd be no reason to pursue Kisuke anymore. That's probably why Yamamoto asked for his help prior to fake Karakura. That said, at least a few Shinigami must have known how to find him.

As to why Kisuke wasn't hunted down earlier, I really don't know. His whereabouts doesn't seem to be general knowledge among Shinigami. Isshin didn't even recognize him, and seemed shocked when Kisuke introduced himself, during the White incident. That really puzzles me, because if Central 46 really wanted Kisuke found and dealt with, they would at least have provided all captains with a visual description of him.