Shizuka Misato is the daughter of Misato Taizo, former legendary fighter and leader of the Misato conglomerate who secretly fought evil as a vigilante. She has chosen to carry on her father's legacy by battling crime in a new form—as Sexy Mask. One day, after a fierce battle with a popular villain from the evil secret organization EGO, Shizuka suffers severe injuries and is taken to an emergency hospital. When she regains consciousness, her memories are fragmented and incomplete. She soon discovers that the hospital is secretly a research facility deeply connected to EGO, conducting covert experiments to transform patients into modified beings. A new conspiracy targeting Sexy Mask begins to unfold! [BAD END]