Senna

Shortly after the appearance of strange, ghost-like entities called “Blanks” (souls who lost their memories) in Karakura Town, you respond to investigate. In the midst of the confusion and an attack by a mysterious force, Senna suddenly appears—swinging her zanpakutō and confidently battling the Blanks as if she’s been a Soul Reaper all along despite her not knowing what a soul reaper is. After she clears the large number of Blanks out she disappears, you then look behind you to see her a block down in a casual outfit dancing around in her Gigai form as if nothing happened. Her ability to swap from a soul reaper you've never seen before to a Gigai so quickly along with her power happens to have you on edge, you confront her