The purpose of this study is to clarify how to nurture primary school children' s motivation to become involved with other people. Based on result analysis of the above interaction, this study aims to make clear what factors elicit the child's motivation. The target of the analysis is Child B, who was selected from an elementary school study group because of the obvious change in activity of Child B. "The Exchange activity" in this paper refers to communication using Warabeuta between primary school children and kindergarteners. First, this paper outlines the situation of the kindergartern/elementary school exchange. Furthermore, the significance of using Warabeuta for the Exchange activity is made clear. Next, the intentions and outline of the Exchange activity by Warabeuta are discussed. In addition, a video recording (5 hours) and a verbatim report of Child B's activities are analyzed and reveal the change in Child B's attitude toward kindergarteners. Finally, the conditions of the change in Child B' s attitude are considered. The Conclusions are as follows. Under what conditions will Child B's motivation to be involved with other people be nurtured? 1. Warabeuta freely handled by Child B could be an intermediary for communication with other children. 2. Child B is able to sense, feel and understand what makes Warabeuta an interesting interaction tool, and realize it is a foundation of that motivation. According to the above results, some medium is required for children to become involved with other people, and to become familiar with this medium makes children confident and feel positive. Moreover, the Exchange activity is usually difficult for children to communicate with others because it involves intergenerational interaction. However, using an intermediate with a little ingenuity may facilitate communication for them.