>>283422933
All I can find so far is this synopsis from the movie's website (just the premise, no detailed plot spoilers):

Can zombie idols save Saga—and the world!?

In the year 2025, Earth is abuzz with excitement over the Saga Expo. Franchouchou is appointed as the event’s ambassador and begins preparing for the main event: a grand live performance at the SAGA Arena.

But suddenly, a massive spaceship appears in the skies above Saga and launches a full-scale attack across the prefecture. The members of Franchouchou are thrown into panic. Is there really nothing ordinary idols can do in the face of such a crisis...?

Just then, the legendary Tae Yamada—the only one who hadn’t regained her self-awareness as a zombie—awakens. Declaring her departure from Franchouchou, she heads alone into enemy territory to put an end to the invasion.

Can the now-splintered Franchouchou come together once more, restore their bond, and save Saga!?