 If you liked
100% Perfect Girl
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 ...then you might like
Ouke no Monshou
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The similarities and purely due to the stories, and in no way are related to the art styles of the manga/manhwa. The Royal Hieroglyph has been published since the 70's, and so it has the distinctive older shoujo manga art style that may turn off some readers.
However, both stories feature the heroine falling in love with a royal (albeit from different periods) and facing a lot of drama in their new lives, whether it be continuous kidnappings, bouts of amnesia, or people simply hoping to steal the girl.