Abstract
Oriza Hirata is renowned in Japan for his promotion of contemporary colloquial theater theory and his distinct style of directing from the 1990s. With Hirata's conducting workshops in Asian, European and North American countries, receiving commissions from overseas, and collaborating with foreign directors, contemporary colloquial theater theory is influential not only in Japan but also outside Japan. He began to use robot actors, and created and directed robot theater series after being employed as a professor in Osaka University where robotics research has an international reputation. I aim to analyze the relationship between Hirata's robot theater and his contemporary colloquial theater theory. To accomplish this I delineate the origin and development of contemporary colloquial theater theory and characterize Hirata's ideas about theatrical reality as well as features of his theater performance. It is argued that Hirata's robot theater series embodies principles of contemporary colloquial theater theory. However, the colloquial style of robot actors which complies with contemporary colloquial theater theory has its pros and cons. It successfully creates a touching performance; nevertheless, possible issues arise concerning the creation of characters of the robot actors.