What you already knows determines what you consider "easy". When you learn English, Italian, Spanish and French you are not learning really 4 different languag

What you already knows determines what you consider "easy". When you learn English, Italian, Spanish and French you are not learning really 4 different languages as those languages overlap each other, they are from the same family(English is part of the germanic[anglo-saxon] but also the Latin family[normand]). If you are native English speaker, you will learn French easily as most of english vocabulary(more than 60% of adjectives, and adverbs for example) comes from French. As a native Spanish speaker, I understand most Italian and Portuguese with little effort, and French only problem is pronunciation, reading it is very easy. For a Chinese native(Mandarin or Cantonese), learning written Japanese is easy, almost trivial. I find Hiragana and Katakana easy to learn, not different from a vocabulary. It is kanji what is harder.