I am absolutely disgusted with the community in the Japanese Language section. I have no interest in participating here anymore, and I don't even want my posts associated with this community. How can I remove my account and posts from Japanese Language, while not losing my account and posts on other stack exchange sites?
In the contact form, pick "I need to delete my user profile" from the dropdown and fill out the rest. Only your account on Japanese Language will be deleted, the accounts elsewhere on SE will not be affected.
However, your posts will remain. You have agreed
that all Subscriber Content that You contribute to the Network is perpetually and irrevocably licensed to Stack Exchange under the Creative Commons Attribution Share Alike license. You grant Stack Exchange the perpetual and irrevocable right and license to use, copy, cache, publish, display, distribute, modify, create derivative works and store such Subscriber Content
The posts will no longer have your username under them, it will be "user19929" instead.