Several days after the battle with the succubi, a location resembling a gate to the succubus realm is discovered, and an investigation becomes necessary. However, Hayato and Sayaka are on a date, and Sayaka is away on a vacation trip. With no combat personnel available, the person identified by the AI is Saiba from the accounting department. Reluctantly, Saiba goes to investigate, but she cannot escape the clutches of the succubi and gradually falls into a trap of lust. That’s the gist of it.