The political marriage of Elma, orchestrated by Terune from the Harmony Force Number 2. Contrary to Elma's smooth acceptance, Kobayashi-san and Tooru, who are still dissatisfied, take the time to reaffirm their respective positions, relationships, and feelings that they have built up until now. And they arrive at one answer. At the moment they realize they can no longer go back, what is the true nature of the sound that resonates in the ceremony hall...? The highly popular non-human comedy, Volume 12 is [Elma's Marriage Arc]!