1. I Want to Be You, Just For A Day Webtoon
2. The Lady and The Beast
emperor and the female knight
If you are okay with colourful ones here some completed ones
http://www.mangago.me/read-manga/second_to_none/
http://www.mangago.me/read-manga/light_shadow/
http://www.mangago.me/read-manga/taming_a_tomboy/
http://www.mangago.me/read-manga/the_lady_and_her_butler/?aeTR
http://www.mangago.me/read-manga/empress_of_another_world/
http://www.mangago.me/read-manga/appetite/
Also here some more straight romance webtoons (random plots, completed ones)
http://www.mangago.me/home/mangalist/685444/
Looking for a romance story with a strong female lead.