Internet traffic at a given web server often increases sharply within a short time as the number of Internet users increases. This phenomenon is known as a flash crowd. When flash crowds occur in the web server, the response rate decreases, or the web server may crash as the load increases. We propose a load reduction system that prevents excessive accesses to the web server in order to stably deliver content without having to enhance the performance of the web server. In the proposed system, the web server detects flash crowds by monitoring the number of requests and changes its content delivery system. To limit excessive accesses, the web server redirects requests to other clients that hold the content in their cache when flash crowds occur. We implemented the proposed system and verified its efficiency through experiments.