In episode 11 of korean series “The King’s Affection” --historical romance situated in the 15th c.-- several characters appear eating corn. Not mentioning it as such, but the images are unmistakeable. Is that accurate?
If the protagonist was born in 1461, then no, it’s not accurate, the arrival of maize in Korea (from China) is later than that - middle-16th C.
By my understanding, they’re off by about 100 years because corn/maize wasn’t introduced to Korea until the mid-to-late 16th century. And even then, it was more of a backup crop than a staple.
ETA: Or what MrDibble said.
Yes. Subsistence peasants paid taxes in rice. They had no choice but to focus on rice. (Rice also had the advantage of being more sustainable even when grown intensively.) Other crops, traditionally barley, were eaten when the rice harvest was not abundant enough to both pay the taxes and feed the family. Maize was used as a back-up, just as barley.
Isn’t the word “corn” sometimes used as a catch-all for grains? A similar question came up about an episode of I, Claudius that referenced “corn”.
ETA - I missed that there is a visual depiction.
You are right that “corn” means (or meant) any grain in British English. “Corn” also could mean a kernel of any substance - “corned beef” is made by preserving beef with kernels (“corns”) of salt, and “corned gunpowder” is gunpowder made into kernels.
What we need is a precocious and unbearably cute PreColumbian kid speaking about corn:
I just watched the series. There’s definitely anachronisms, and not just with corn. There’s also a mention of eating potatoes and sweet potatoes. Those mentions took me out of the show for a few minutes 
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