This paper proposes an interactive manager agent system that adjusts schedule among multiple persons through negotiations on behalf of a human organizer, such as a steward or team manager. In order to increase the users' cooperative decision-making, we implemented the manager agent that negotiates with each member on the schedule using 1) the suitable attitude depending on current situation and partner of negotiation and 2) the graphical representation of background negotiations between the agent and the other users: a) the other users' icons, b) the blinking balloons of both the other users and the agent, and c) the agent's looking-back actions for the other users' icons. The results of the evaluations showed that both the individual use and the combination of the proposed expressions could make the participants feel i) as though there were under-going negotiations between the agent and the other users and ii) as though the agent had both the effort and compassion to the user. Moreover, the user's cooperative decision-making was increased by the proposed method.