100 Days My Prince (2018)

Both have a rich main character that lives in a village
Both main characters have a secret they’re hiding

But I think that’s all there is with the similarities

-male lead is a prince in both
-both have male leads with strong personalities that do not sit well with others, and are seen as a royal pain
-both male leads are extremely smart
-both couples have met previously as children
-both female leads are maiden /spinsters
-both have the plot line where should be "enemies" fall in love
-both female leads are tough and fight for themselves
-both have a best friend solider dynamic
-both have the main couples separated for a period of time
-both have dead ends for any second lead storylines
-both include assassins
-both have parental deaths
-both have an arranged/forced marriage
-extra- both have a celebrity singer acting the lead male role lol
-the "happy ending" focuses on the main couple

Both have similar vibes and a sweet romance that transcends class (and time) along with palace intrigue and dangerous enemies.

Rookie Historian is not completed yet, but it already reminds me of this drama not just for the time period, but the strong female lead and prince pairing. Both are also noona romances which is a bonus. :)