Contact
There are a number of options for getting in contact with responsible people for GNU social JP.
Bugs
If you think you've found a bug in the underlying GNU social software, or if there's a new feature you'd like to see, add it into the GNU social task list. Don't forget to check the list of existing bugs to make sure it hasn't already been reported!
You can reach the responsible party for this server at contact@gnusocial.jp.
Post a notice
If you have a question about how to do something, just post a notice with your question, preferrably tagged with #NewHere. Watch your inbox for replies.