With the aim of creating an energy-efficient, green, social and flexible urban living environment fit for the challenges of the 21st century and its demands, Osaka Gas commissioned the experimental residential complex NEXT 21 in Osaka (completed in 1993). 15 years into its existence and after three consecutive five-year cycles of ongoing inhabitation experimentation, the documentary looks back on the context and conditions of its pioneering multi-disciplinary design process. Interviews with: Yositika Utida, Seiichi Fukao, Mitsuo Takada, Hiroshi Horiba, Shinichi Chikazumi and John Habraken.