Kogure Kounosuke, a strong-willed weapons designer for Takeshi, comes bearing a gift for the Oni who work at the Tachibana Sweet Shop: the Armed Saber. Unfortunately, the weapon is too powerful for a normal Oni and the repercussions for trying to use it is losing the ability to transform. But when a new Douji and Hime appear more powerful than any before, the Oni may have no choice but to risk using it in battle