Thieves lurk at a high society party hosted by a jeweller. Their target is an alexandrite ring called “Alexander's tear” and said to be the the best jewel among jewels. Kamimura Rei has been recruited by Nishizaki, the butler of a mysterious woman called Kitaba Yoko, to steal the ring. Katagiri Karen and Kishihara Taiga have each been recruited for the same purpose too, and they plot to get close to the target.