User blog comment:Xilinoc/Ch. 647 - THE THEATRE SUICIDE/@comment-10301320-20151015071619

Early speculation on this Bankai is that it has some kind of voodoo mechanism for anyone caught in the area, with the part of Shunsui's shadow copy doing the killing of people. Alternatively one of those patterns of darkness semi-resembled a volcano to me so maybe THE FLOOR IS LAVA. Also a stage play is kind of a more adult version of children's imagination games like "playing cops" and whatnot so the theme is preserved if it does end up being based on that Japanese play you linked. Speculation over.