The number of users of VoD services in which users can request content delivery on demand has increased dramatically. In VoD services, the demand for content changes greatly daily. Because service providers are required to maintain a stable service during peak hours, they need to design the system resources based on the demand at the peak time, so reducing the server load at the peak time is an important issue. Although multicast delivery in which multiple users requesting the same content are supported by one delivery session is effective for suppressing the server load during peak hours, the response time of users seriously increases. A P2P-assisted delivery system in which users download content from other users watching the same content is also effective for reducing the server load. However, the system performance depends on selfish user behavior, and optimizing the usage of system resources is difficult. Moreover, complex operation, i.e., switching the delivery multicast tree or source peers, is necessary to support VCR operation. In this paper, we propose to reduce the server load without increasing user response time by multicasting popular content to all users independently of actual requests as well as providing on-demand unicast delivery. Through numerical evaluation using actual VoD access log data, we clarify the effectiveness of the proposed method.