Kuroko seems to be one of those "too kinky to torture" types, but I'd much rather see her enjoying herself in any case. With her teleportation ability it's unlikely (although possible in a few cases) that she is in a bondage getup against her will. Maybe she set up one of her pervy attempts to get intimate with Mikoto, and she's getting bored from waiting for Mikoto to get back to their dorm room.