Can't decide the story T^T....Either:
Story 1-It's Mia's reiai appearing at night in front of Toshiro asking him to kill her so she doesn't have to be forced to hurt him.
Story 2-An illusion from Aizen before Karakura town arc happens and it's Mia and she says "Shiro-kun,you'll never hurt me right?Help me Shiro-kun!"and Toshiro replies,"Aizen,you bastard!"Also base credit to Mikari :3 This took me forever to edit -.-"