Except for all the exceptions. Also, the millions of different ways you need to manipulate your verbs based on what comes after/what you are talking about.
Oh, and that you cannot read/write contemporary Japanese without knowing at least 3 writing systems (with a minimum of 54 characters each).
Japanese grammar was pretty easy for me to learn. There are only three verb groups in Japanese (i.e., Godan, Ichidan, and irregular verbs). The irregular verb group only has two verbs する and くる. The others are pretty consistent in following a few simple rules that map quite cleanly into a spreadsheet. There are 14 conjugation forms, which seems like a lot at first, but again, the rules are pretty consistent and easy to learn. At least I think so.
The hardest part of learning Japanese for me was Kanji (which I still forget all the time if I’m not using an IME or a dictionary).
Except for all the exceptions. Also, the millions of different ways you need to manipulate your verbs based on what comes after/what you are talking about.
Oh, and that you cannot read/write contemporary Japanese without knowing at least 3 writing systems (with a minimum of 54 characters each).