Japanese kanji are pretty different from hanzi

No, they are extremely similar. It's the same system. The hardest hurdle for speakers of other languages is getting used to a different type of word recognition, which Chinese speakers do not have to do. Even the ones that have been simplified differently are very recognizable with a tiny amount of exposure. And the multiple reading thing is way overstated. I usually just see it used as an excuse for not actually reading or listening to the language.