Bump
I just want to post on 5ch and futaba channel

Have you already tried the VPN by Tsukuba University? I think it is called SoftEther or something. I used to use it when I was living in the states so that I could access Abema which is a Japanese streaming site. It is completely free but you might have to try a few servers before you find one that works or isn't detected by the site you are trying to access.