There was an error in my discourse, which I couldn’t add a specific tag.
I knew that using a double byte parenthesis in a tag, which Japanese keyboard has caused an error.
So, I changed it to a single byte parenthesis.
After that, however, I couldn’t use that tag anymore.
There was the tag in the tag page. If I clicked it, the message -no page was found- was shown up.
So, I thought that I should add the tag to each post manually one by one from scratch.
However, this was not possible since Discourse showed an error message and didn’t allow me to save the post with the tag. Maybe the tag still exists somewhere.
I would appreciate it if someone could share how I can solve this issue.