“chaika” for Firefox enables you to turn your Firefox browser into one that functions properly with 2ch.net, Japan’s largest textboard website. Among the features that it includes are optimized views of threads and boards and a seamless connection between general web pages and 2ch-dedicated views. You can also choose to have content that is deemed objectionable blocked by the Intelligent NG system.
More information about the extension and 2ch.net are available on 2ch, which features a thread dedicated to this add-on, and Github. Both resources are available in Japanese.