User blog comment:Xilinoc/Ch. 543 - Letters/@comment-5462417-20130628051914

Im starting to believe the body mayuri was experimenting on is one of the stern ritter that fell to kenpachi or some other vandenreich instead of kira as many people are believing... that would explain the spoiler of the arc and frankly it makes more sense since it is best to identify the enemy weakness before they strike back.