Language barrier? Who gives a damn?
I'd have to say, it is quite an interesting change to go from English to Korean so suddenly.. But I for one enjoyed it just as much, if not more, this way. If you and your voice actors have an easier time working using Korean scripts, rather then English, then honestly, I say go for it my friend. Having to read subtitles is a very very small sacrifice to have to make, when getting to watch these fantastic movies.
I am quite eager to see the next one, keep up the good work, and ignore the ignorant imbeciles that try to put you down for any reason... I thought the English voice acting was good, and I think the Korean voice acting is great too, I honestly don't know why some people try to act as though the barrier between different languages is such a huge impact on things. Just because the characters are speaking in a foreign language, and you don't understand them, doesn't mean you can't recognize what they are trying to say, by paying attention. Plus, you provided Sub Titles, to make it even easier to understand!
Once again, fantastic work on your series, keep it up, and good luck to you on your future videos, I await eagerly to see them.
-Cossack.