If we assume “Maron x Master Roshi” is a real fan short, here is a likely 3-act structure based on common fan parody tropes:
The phrase signals that the video includes translated dialogue for non-Japanese speakers. However, in fan circles, “Full English Sub” often means the uploader added their own humorous or dramatic subtitles – not a literal translation. Think of it as a used for comedic shipping. Maron x Master Roshi -Full English Sub- -Chucho...