![](https://i.mydramalist.com/letter/12887471)
FayeB:
I don't think its splash splash love because the king is called King Lee Do and I think she teaches him math and science rather than hangeul :(
Have you watched Splash Splash Love? It's been years since I've seen it, but I believe she does teach him different subjects before she finally teaches him hangeul. And his name is listed as King Se Jong in the cast list even though the one in the synopsis is different.
I mean I still could be wrong, but I still have a good feeling it's the one you are looking for.