It strikes me as a problematic oversight that I've never read "The Prince and The Pauper" but have watched many an adaptation on TV and am now reading a shonen manga version of the tale. I really do need to read that book one of these days.
That being said, this seems to be a fun interpretation. Astro (I know, I know. It's a fighting manga. Go with it) is a young orphan with a home full of even younger orphans who make up a ragtag family he's fiercely devoted to. After a run-in with a foreign (as in, from off-planet) noble, he catches the eye of Prince Barrage, who proposes that the pair switch places. This turns out to be a mixed blessing for Astro, as it does take care of the question of how to care for his family - but it also forces him to expand his definition, as the prince is charged with bringing peace to the land.
The art in this manga is really expressive, and I think the story has a good flow, even if it's a little on-the-nose at times. (Yes, Astro, we KNOW family is the most biggest, bestest, importantest thing in the whole world and people belittling it makes you angry. WE KNOW) but it's cute, and a little bit dark, and overall a pretty enjoyable manga. It helps knowing that the manga is limited in length - only two volumes, meaning it's not a big investment of time.