If you’ve only seen a clip of this game, I understand the confusion. I’ve played the whole game and honestly, I’m not 100% sure it wasn’t just a fever dream.
The game opens on the King of All Cosmos accidentally destroying all the stars, the Moon, and pretty much all celestial bodies except for Earth. You play as his son, the Prince. He gives you the responsibility of replacing these missing stars. The big problem is you are 5 CM TALL. Soooo to help, your dad gives you a katamari, a magical ball that will roll up anything smaller than it. Thanks, dad.
The basic gameplay involves you running around with the katamari, rolling up anything you can to make the ball a specific size before the time runs out. After each level, your dad puts the ball into the sky, replacing a destroyed celestial body. You eventually win the game by rolling up a HUGE katamari and replacing the moon. I promise it makes sense.