Takagi was born in Gunma Prefecture in Japan in 1938. After graduating from the University of Tokyo in 1961 he worked at Nippon Atomic Industry Group (NAIG), the Nuclear Institute at the University of Tokyo, and at Tokyo Metropolitan University as an Associate Professor of nuclear chemistry. After spending a year at the Max Planck Institute for Nuclear Physics as a Guest Scientist he joined with a group of colleagues to create in 1975 the Citizen's Nuclear Information Center (CNIC). With his leadership, CNIC undertook its numerous research and public activities as "Citizen Science." Takagi received Yoko Tada Human Rights Award in 1992, the Sankei Children's Book Award in 1993, the Ihatobe Award in 1994, Tajiri Award of Tajiri Muneaki Memorial Fund and the Right Livelihood Award (jointly with Mycle Schneider) often referred to as the 'Alternative Nobel Prize in 1997 and in 2000 Peace Award of the Nagasaki Prefecture Association for Friends of Registered Hibakusha.
The Right Livelihood Award in 1997 (Joint Award with Mycle Schneider)
Citizen scientist' fighting on / by Mayo Issobe, Asahi evening News, 1999
The Life of Gusukoh Budori / by Karen Colligan-Taylor, Masterworks of MIYAZAWA KENJI, 2002