He became involved with left-wing movements while attending Tokyo Imperial University.
He was editor of the Red Flag (Akahata)[2] and a member of the House of Representatives.
During his time in the National Diet, Shiga was in favour of the Partial Nuclear Test Ban Treaty.
They later established a pro-Soviet Communist Party known as the Voice of Japan.
[2] Yoshio Shiga appears in the docu-drama "Nihon no Ichiban Nagai Natsu" (“Japan’s Longest Summer”).