Well it is not really a bug, maybe sort of...How can one delete his membership at MiniTokyo? I have not seen this option anywhere.

Why would you want to? If you want to leave then you can leave. If you feel like coming back then you can come back without having to make a duplicate account & start all over again.

You can't delete your membership on MT. If you don't want to use your account anymore, then delete all of your gallery items, posts etc, change your password to something totally random, log out and clear your browser cookies.