User blog comment:Xilinoc/Ch. 580 - THE LIGHT/@comment-3250274-20140514164652

So my thinking as to who has shown up could be any of the few mentioned here. Yachiru, because the skull reminds me of the cat shaped pink reiatsu she released; maybe foreshadowed by her new cross bones head accessory. Ichigo because of course, its a skull; thought I doubt and hope its not him. Ginjo Kugo, because the skull is similiar to the Substitute Shinigami badge. To quote Will-O-The-Wisp below, "The explosion was definitely caused by breaching the Shakonmaku, so it's either Ichigo or the Fullbringers, sent there by Kukaku's cannon." Grimmjow and crew because it's about time. Neliel is a possibility as well imo. I think Unohana is a bigger stretch than some of these.