The need for the design of human interaction arose since the relationship between human manipulation on tools and their response had become ambiguous along with the developments of tools and machines. The goal of human interface design is transparency. The transparency is a condition in which a user can concentrate to solve a target problem, without being aware of the tool itself, and the tool feels like a part of the user's body. However, the realization of the transparency has been only discussed as idealistic theory, and the design methods have not been discussed enough. In this paper, we introduce “dummy cursor experiment” and “sense of self-ownership.” We also consider transparency of tools, extension of body, and differences between the animation for expression and the animation for manipulation on user interface design.