In this paper, we discuss the behavior of a companion robot, which lives symbiotically with humans and makes good impressions on them. Its behavior, rather than its appearance, is emphasized. Inter-human behavior is analyzed through a simple simulation environment using two networked PCs. A red ball and a blue ball are displayed on each simulation screen. One person moves the red ball; the other person moves the blue one. Next we design inter-human behavior based on the pattern, transition, trajectory, and velocity. The programmed behavior is verified using a Turing test: the test subject guesses which behavior is generated by a human. Finally, we examine the impressions of the real robot SELF and the AIBO robopet (Sony Corp.). The result shows that SELF's impression, considering human interaction, is superior to AIBO's in terms of the evaluation items of "interesting," "not boring," "attached," "want to be together," "healed," "want to play again," and "favorable."