They also announced that the premiere will happen June 14. This was originally scheduled to air in December 2023, but was delayed for unspecified reasons. There is a PV available here. Though this movie is, I believe, a spinoff story, it is based on a previous show, Tsukiuta, which is where I pulled this AniList synopsis:

Six Gravity and Procellarum are two rival male idol groups who happen to live in the same dorm. Six Gravity is made up of young men who represent the months of December to May, while Procellarum’s members represent June to November. Follow the daily lives of these twelve young men as they deal with the stresses of idol-hood, school, and living together. With music by famous Vocaloid producers!