Rukia Retaliates! Release the Desperate Kidō

Tracking Rukia's climbing Reiatsu, Renji is startled by Dondochakka before racing onward in worry. Inside Aaroniero Arruruerie's palace, Rukia trades blows with the figure of Kaien Shiba, finding herself outmatched as he mirrors her own Sode no Shirayuki dances and even releases his trident Shikai, Nejibana, against her.

Sensing her friends fighting elsewhere, Rukia refuses to accept that this is truly Kaien. She recalls that he only shed his mask after moving indoors, and gambles that sunlight will break his disguise. Binding him with a double incantation and firing Sōren Sōkatsui through the wall, she lets daylight pour in, melting the Kaien facade away to expose a glass capsule holding two floating Hollow heads.

Aaroniero explains that as the sole Gillian among the Espada he alone possesses limitless evolutionary potential, which let him absorb Metastacia's Spirit Body Fusion by devouring the creature and thereby wear Kaien's genuine spiritual body and memories. Reforming Kaien's head within the shadows, he declares the duel over and activates his Resurrección, Glotonería, rearing a monstrous blob-like mass over the stunned Rukia.

Rukia deduces that sunlight neutralizes her opponent's power and uses layered restraints plus Sōren Sōkatsui to strip away the Kaien disguise. Aaroniero's true form, twin Hollow heads sealed in a fluid-filled capsule, is revealed. He explains that consuming Metastacia let him steal Kaien's appearance, memories, and abilities, then unleashes his Resurrección, Glotonería, to end the fight.

The 155th episode covers the back pages of chapter 265 through chapter 267 in the first Hueco Mundo arc. Its Arrancar Encyclopedia segment has Gin Ichimaru introduce the small Hollows of Hueco Mundo before stabbing Bawabawa from within using Shinsō. Anime additions extended Rukia's clash, her memories of Kaien, and softened much of the manga's blood.