© 2017 ACM. With the development of Web 2.0 technology, Q&A websites have become one of the most common avenues for large scale knowledge sharing. However, three types of barriers between questioners and respondents make knowledge sharing difficult: differences in the personality types of the questioners and respondents, lack of trust, and an arrogant or negative attitude exhibited by some questioners. In order to lower these barriers, we propose a Q&A mediator system with virtual character agents. In this system, a questioner asks questions through his/her own agent, and the respondents see the question from their agent. Each agent has four characteristics: personality traits similar to knowledge sharers, good looks, affable personality, and a positive attitude. The results of a preliminary experiment indicated that the proposed system can improve the users' motivation to answer questions.