We first point out a problem in the role casting method of a story generation system called OPIATE and then propose a solution to this problem. The existing casting method does not take into account the emotions of a cast non-player character towards actions that it must perform in its role, leading to a miscast. In the proposed casting method, such emotions are considered, besides emotions towards other characters as done in the existing one. Evaluation results, using an online-game simulator, confirm the effectiveness of the proposed method over the existing one with respect to the number of miscasts.