There is a river near my house and never caught a bass there, I asked a person casting next to me, he said the bass here are small and there are only about 10 bass in the area. Is there anything I can do to catch these small bass or do I have to use the same lure I use for big bass

You can always down size. Example, if you use a 6 or 8" worm, try a 4" worm. Also, you may want to, if you haven't already checked youtube in Japan, there are a lot of good videos to learn from.

I live in Kyushu where there are a lot of snakeheads. I found more production with trying to catch snakeheads and catfish where I live. I’d recommend going for snakehead.