The Japanese language uses a separate syllabary known as katakana to spell loanwords from foreign languages. It is therefore often fine to literally translate these words into English. オレンジジュース (orenjijuusu) becomes orange juice, and ホットドッグ (hottodoggu) becomes hotdog. However, this is not a viable translation strategy for every katakana word. First, there are words that originate from languages other than English, such as デッサン (dessan) which comes from the French word "dessin", the word for a drawing. Second, there are Japanese words that are constructed from elements of English that would be nonsensical if translated back into English, such as マイブーム (maibuumu), a word used to describe something that you've recently got into/obsessed with. It goes without saying that it would be incredibly strange if a character in a book said, "My boom is tennis."
