User blog comment:Primeramizery/What could Mayuri be working on in his lab?/@comment-4207271-20130709084205/@comment-8840393-20130710062739

i doubt it's Unohana or Kira.. chances are, he's creating a monster of some sorts. Unohanas bankai will probably be explained later in the story and if Kira were to still be alive, he would have been healed by the 4th company.. though it would have made more sense if he were a part of the group that went to the the soul palace since his injuries were that severe..