Well first vocabulary is definetly a hard part Second i would say is pronunciation and third actually being able to practice its like an instrument, that you need two people for its kinda impossible without a second person to correct you and just having the actual resources, and lastly when its a language from a country across the world to me its gets tough just trying to talk to people Anyway thats my thoughts on learning japanese I do love it though i managed to stutter my way through a conversation and people when you put in the effort are awesome.