Not much is known about the planet Koppai other than it having a single moon and that it's about 279,000 Lightyears away from PNF-404. This kind of distance suggests that Koppai is located outside of the Milky Way Galaxy, as it is only 100,000 light years long. This suggests Koppai (and maybe Hocotate) could be situated in one of the many "Mini Galaxies" clustered around the outside rim of the Milky Way Galaxy. Its surface is never seen or described in-game, but the opening cutscene seems to imply that the planet has a very thick atmosphere, covered in large masses of clouds.