Creation of scent suited to each user will contribute for more efficient aromatherapy and use of scent in daily life. We have already proposed Interactive Differential Evolution (IDE) that creates user scent and have demonstrated the evolution of scent. In the proposed method, simple paired comparison between two scents was corresponded to comparison between target and trial vectors in general Differential Evolution (DE). However, detail observation of DE's vector in the proposed method was not performed. This study investigated change and convergence of DE vectors in the proposed method. The investigation will contribute to develop more effective algorithm of IDE.