The current General Megathread reminded me of this band. From the Wikipedia page about them:
"Although the band itself was not overtly political, original and early members were known to participate in various political organizations and movements amidst the volatile daigaku funsō and Anpo protests of the time, with the band as a whole reportedly performing in the occupied Kyoto University auditorium while it was held by students during a protest in 1969, this event being known as the "Barricades A Go-Go concert". The band also performed at political concerts around Japan, including a Kyoto University concert on Gozan no Okuribi protesting the construction of the Sanrizuka airport.
In 1970, after having performed with the band since 1967, original bassist Moriaki Wakabayashi assisted in the hijacking of Japan Airlines Flight 351 orchestrated by the Communist League's "Red Army Faction." He was known to be engaged in political activity by the rest of the band, but Wakabayshi himself claimed the band never really talked about politics amongst themselves. Mizutani is cited in Susumu Kurosawa's book "Psychedelia in Japan" as saying "Sometimes we hold a guitar, sometimes we hold protests, variety is good, but protest songs are a bore."Wakabayashi and Julian Cope both claim Mizutani attended political rallies with a black helmet, implying he was an anarchist."