In Hiroshima, just a couple hundred yards from ground zero, there's a clock that counts the days since the world's last nuclear test. Today it was turned back to one.
But a second clock, marking time since Hiroshima was hit, keeps ticking. And as survivors gathered to protest North Korea's nuclear test, it was clear that 61 years and 65 days later, no one here has forgotten.
Eighty-one-year-old Sunao Tsoboi survived the U.S. attack in 1945, though he was standing just a mile from ground zero. Today he still bears the physical scars as well as a deep-seated disgust for nuclear weapons
"North Korea's test is unforgivable," he said. "It angers me so much. I'm sick to my stomach."
Japan is a country devoutly opposed to nuclear weapons. And in Hiroshima, it is easy to find people with extremely personal reasons for their opposition. On a bridge overlooking the famous A-bomb dome -- the iconic remains of an industrial building that somehow withstood the blast -- we stopped a bicyclist to chat and learned he was a survivor as well, 4 years old at the time of the attack.
"North Korea is like a child walking in adult shoes," he said. He also called North Korea's nuclear test "unforgivable."
"Japan has two very good reasons for a nuclear allergy," said Jeff Kingston, a professor at Temple University Japan. "Hiroshima and Nagasaki," the site of the second atomic bomb attack three days after Hiroshima.
But North Korea's test, coupled with missile tests in July aimed at Japan, has sparked a question long taboo here: Should Japan itself go nuclear?
"Japan will be adopting a more aggressive military posture," said Kingston. "I expect that it is going to build up its military forces -- conventional ones. I don't expect that Japan is just going to sit here and do nothing. I think that the prime minister will be under political pressure to respond and appear to be responding."
Japan has already shed some of the pacifism it adopted after its humiliating defeat in World War II. In 2003, it decided to build a missile shield and, in 2004, it sent troops to Iraq, its first foreign deployment in 59 years. Now the newly elected Prime Minister Shinzo Abe is calling for an even more assertive Japan.
Still, only a small, nationalist minority wants Japan to build its own bomb. At the site of the world's first nuclear attack, just the thought of the bomb is unsettling.
When asked if he's worried there will be people who say Japan now needs a nuclear weapon to protect itself, Tsoboi answered, "I'm amazed you would even ask. That would be such a terrible departure from the peaceful nation we want to maintain."