Kadokawa began streaming a promo for the video, which showcases Subaru, Rem, and Ram telling Emilia that they are making an OVA. White Fox is returning to animate the short project, and the previous voice cast will be reprising their roles.
While not confirmed, the trailer heavily implies that the OVA is an adaptation of the “mayonnaise” side story. It’s exactly as it says on the tin: Subaru, Rem, and Ram spend the day making mayonnaise. The side story takes place between episodes 10 and 11, and it explains why Rem becomes attached to Subaru.
White Fox will announce a release date and story details at a later time.