The Queen's Knight by Kang Won Kim 17 volumes- complete
The troubled Yuna escapes to Germany to get away from her issues in Korea. There Reino whisks her to Phantasma to be his queen. The foreign queen and her knights holds the key of unlocking the curse of the land. The story unfolds very slowly but the mystery was well thought of. Thanks to an anonymous visitor via comment and skribit for the tip!
For other titles of heroine taken to another world, well besides Fushigi Yugi and Harutoki, you can try Red River and Meru Puri.