Worst One Piece movie/film ever. They really just made a character and forced the entire One Piece world cater to her. The pacing was all over the place and the plot is really bad. Music is amazing though!
*SPOILERS*
Uta essentially tries to make a "New Era" by broadcasting herself worldwide and singing at her concert. She has a demon fruit ability that can put people to sleep and transfer their souls to her dream world when she sings. This affects everyone, including over the radio or them watching through the TV. The 2 hours is just her singing and trying to convince everyone to stay in her dream world where they never have to work and can have fun. Eternal peace.
How she intends to do this is trap everyone inside her dream world as she overdoses on mushrooms that keep her awake until she goes crazy and dies. If she dies, everyone is eternally trapped in the dream world. That's it. Her backstory is garbage as well and it doesn't even justify trying to end the world. Don't bother watching. Just listen to the music on YouTube/Spotify and support the artist! :) 👍