User blog comment:Xilinoc/Ch. 618 - The Dark Arm/@comment-11446176-20150305123333/@comment-11446176-20150306022236

well, if its the keys to Muken it makes more sense... or less if you consider he just told Aizen that the keys to get out were in his body, and if he wanted to get out, he needed to get it out of Shunsui....

Oh, and RE: Aizen standing next to Yhwach... Yhwach feeds off external sources of Reiatsu.... Aizen next to him will just be... Buffet.