World Wide Web contains a vast amount of diffierent infor- mation stored in a huge number of distributed Web sites. Search engines and information agents have been developed to facilitate efficient in- formation retrieval tasks from the Web. By integrating multiple search engines and information agents as an interoperable system, we increase the value of each of them. In conventional collaborative systems, the in- tegration process is designed by system designers and is concealed from the end users. This paper proposes an interactive multiagent-based interface called Mul- tiple Character-agent Interface (MCI) where animated character-agents interact with each other and with the user for assisting in information retrieval. By using the MCI, even a novice user can create a team of infor- mation agents and can self-customize the agents through the interactions with them. We here report the architecture of MCI and two prototype systems based on MCI, Venus and Mars, which is a cooperative multi- agent system for information retrieval, and Recommendation Battlers, which is a competitive multiagent system for information recommendation.