For the personal robot to serve humans as a companion in our daily life, it is obviously important that the robot should have a long-term relationship to users. In this paper, we introduce a simple idea on how to make the long-term relationship by using just low-cost and simple robots. We also describe the robotic artificial creature system to implement this idea. The artificial creature robots respond not only physical environment changes but also the logical information changes in the virtual world such as the Web. They consist of a control robot and several simple robots, which show users various group behaviors. Users have a relationship with them by observing these behaviors, rather than interacting with them. We separate physical robots and software applications in order that artificial creature robots can have more various behaviors made by various software applications. Finally, we implemented the system using a robot simulator to show some example cases.