Well, I saw your video and used CC. The CC in English was automatically generated with Google's voice recognition service and then translated in to Korean with Google Translation service. I personally use a SW which automatically generates subtitles with Google's API, and they are great with English. almost 90% if your voice is clear. I see your audio is very good so automatically generated CC was good too. I think that Korean person who thanks to you may have turned on the translation(EN > KO) without knowing. Here is the result anyway(70% natural) :