Bunken is a cloud-based Japanese writing assistant from Web Rider Inc., a Kyoto-based company known for SEO consulting and content strategy. The tool combines AI suggestions powered by large language models with proprietary rule-based checks covering proofreading (typos, honorifics, trademarks, offensive language) and editing (sentence length, notation consistency, verbose expressions).

Teams can create shared custom dictionaries to enforce consistent terminology and style across departments. The platform accepts Word, Excel, PowerPoint, PDF, and text file uploads, extracting text without storing files on servers. Input text is not used for AI training, and the service operates in an ISO/IEC 27001 certified environment.