Fushigi Yuugi, Arata Kangatari Recommendations
The worlds that the main protagonist ends up in both worlds are far from the modern worlds they come from, yet the conflict revolves around the main protagonist and they find themselves needing to gain power to solve the problem.
The main character is transported to another world. They are chosen/destined to save that world. Same series written by Yuu Watase. Similar themes and art.