Yui and Kikuchi, commonly known as SIB investigators, board the enemy's territory, but when the boss Kurokawa strikes back, Kikuchi protects Yui and marries him. Kaori, Kikuchi's fiancé, blamed Yui and resented him. "It's your fault. I'll take revenge." Kurokawa, who is trying to destroy the SIB, approaches Kaori. Kaori ... was invited by evil.