In late September, amid the lingering summer heat in Hiroshima’s Peace Memorial Park, hibakusha, or atomic bomb survivors, were once again collecting signatures.

Members of seven survivors’ organizations have been taking to the streets every two months for the past four years to urge the Japanese government to join the Treaty on the Prohibition of Nuclear Weapons.

“We’ve long called for there never to be any hibakusha produced again, and that has given rise to a global taboo against using nuclear weapons,” said Kunihiko Sakuma, 80, chair of a Hiroshima prefectural hibakusha association. “But now, we’re at the brink of nuclear weapons possibly being used again.”