You can usually find something on a Japanese search engine if you type "game name (in Japanese of course) + 攻略". 攻略 (Kouryaku) is the equivalent Japanese word used for guide/walkthrough/etc...
Most of the Japanese RPGs that I passed that have no English faqs (Aurora Quest, Burai I/II, KO Seiki Beast Sanjushi, Gulliver Boy, Babel, Nekketsu Legend Baseballer, etc...), I was able to come up with something by searching with the above term.