Planet Blood (1996)

Blurb:
In the year Universal Century 0091, Sinan is a mecha pilot for the Mars colony in its war with the Moon colony over re-patriation rights over the newly restored Earth. An explosion catches him off guard and Sinan wakes up to find that he has been mysteriously transported to an entirely different world called Horai, with a civilization similar to that of Earth’s middle ages. There, Sinan ends up rescuing a girl named Mayi from a group of thugs lead by a burly thug named Pantera. A grateful Mayi introduces Sinan to Noodles, a leader of a rebel group that is trying to restore him to the throne of Pratria ...

Source: www.anisearch.com/manga/668