The spoken grammar of Japanese isn't too bad. I'd say it's more logical than English overall.
Written Japanese in Hiragana and Katakana is unambiguous in spelling/pronunciation. It's not like English where you need to learn a bunch of spelling (and sometimes multiple spellings). So it's massively easier.
There's Hiragana and Katakana which have a similar purpose, but then English has upper and lowercase letters for seemly no very useful reason.
Kanji is a significant additional workload and there where efforts to get rid of it in the past. The problem is I'd guess it does have utility, cramming more data in per unit area is useful, as is being able know it mean "on" or "off" or "of passable quality". And now with computers you can type in Hiragana and it prompts for the Kanji. That makes things significantly easier.
The other thing that's interesting about Kanji is the meaning is divorced from the sound. With English your forcing a discretized serialization on sounds. With Kanji the idiographic communication feels closer to a visual representation of a concept.