Sangaku were media using wooden tablets to exchange knowledge of geometry in Edo period of Japan. We have been studying ICT to resurrect Sangaku as a new media to exchange knowledge of diagrams. This note reports how we used Augmented Reality (AR) to explore some beautiful theorems of geometry related to spheres of Sangaku. It is demonstrated that AR allows manual operations of removing or adding spheres, and continuous transformation of existing spheres, which has been impossible without diagram visualization by computers.