When previewing a Sitecore item, there’s an option in the ribbon to change the language. For whatever reason, Japanese was a given option in the Sitecore installation I was working on. The only language needed for the Sitecore project was English, so any other options would just add unnecessary clutter. To remove this, navigate to the Sitecore > System > Languages node in the Sitecore tree (master database) and delete the ja-JP item.
A John of all trades, but mainly in body, mind, and IT.