Sounds one doesn't encounter in their native language are always hard. I remember when learning Russian in school there was one that's basically "schtsch".
I'm still learning basic Russian pronunciation, haha...
I guess I'm lucky in that growing up speaking Mandarin at home and English everywhere else has given me a pretty good grasp on different, non-Romance-language phonetics and grammar.
I sometimes wish I had been raised in a bilingual household, same as I always wanted a private tutor. Maybe that's why I'm learning so many different "useless" things on my own now, like languages I may not even need for travel. *cough* Klingon *cough*
To be fair Japanese is a walk in the park compared with most languages, at least as far as grammar is concerned. Same as English. And if you're looking for something with an easy vocabulary instead, have a look at Toki Pona.
Oh, yeah, the tonalities...hm. They're interesting. Having grown up w Mandarin, it's pretty hard for me to understand why exactly people have issues with it, but then again, Mandarin/Chinese in general just doesn't really have tenses and such, so that probably lowers the chance of confusion with context.
...I'm trying to pick up some Taiwanese, but, uh... that dialect's got seven (?!) tonalities.
I took Spanish all through high school, but barely have retained it since there's not really a large Hispanic population here to keep me using it. I mainly just remember a few random words and phrases.
I really do want to learn Japanese, but have been....mainly just lazy and haven't worked on learning it at all.