Kuroyoru Umidori is a mysterious girl who apparently is connected to the dark side of Academy City. She poises as an antagonist in Shinyaku Toaru Majutsu no Index Light Novel Volume 01; she is a member of the mysterious organization known as "Freshmen".
She looks down others as evident with her conversation with Kinuhata Saiai and treats anyone as disposable things. Accelerator remarked that talking to her was like having a conversation with his "old" self. She has a liking to stuffed doll dolphins and is always seen carrying one.