Japan and the United States have forged one of the world's most enduring -- some would say improbable -- relationships in the seven decades since American atomic bombs laid waste to Hiroshima and Nagasaki, killing 200,000 people.
The two nations fought four years of searing, brutal conflict across the Pacific during World War II, culminating in the catastrophic destruction of the two cities in August 1945.
But despite the unprecedented carnage, the fiercest of enemies somehow became the best of friends.
Barack Obama is set to become the first sitting US president to visit one of the bomb sites when he journeys on Friday with Japanese Prime Minister Shinzo Abe to Hiroshima, hallowed ground to Japanese but, for more than 70 years, a no-go zone for 11 of his Oval Office predecessors.
There will be no shortage of sensitivities, symbolism and emotion on display, including difficult and contentious questions that have long eluded precise answers: Were the bombings war crimes because they targeted civilians? Or did they save lives by bringing the conflict to a speedy conclusion?
But Japanese rancour toward Americans will be hard to find.
"I have no feeling of hate," said Hiroshima survivor Toshiki Fujimori, who blames then-president Harry Truman for ordering the use of the weapons and says he has no ill will for "America as a whole".
- 'Tolerant occupation' -
The road to the current relationship started not just in the violent culmination of World War II -- the "cruel bomb" described by Japanese Emperor Hirohito in his surrender speech -- but in what came after.
Seven years of occupation spearheaded by General Douglas MacArthur followed defeat, including the imposition of a US-penned constitution that famously stripped Japan of its right to wage war.
But it also ushered in monumental social changes, including the nascent empowerment and liberation of women through the granting of suffrage.
"I think this occupation could be said to be both tolerant and peculiar," said Fumio Matsuo, a veteran journalist who survived an American air raid as a child.
"It was a form of occupation which perhaps had no precedent or similar model in any other country in the world," added Matsuo, who in 2009 published the presciently titled book, "The Day President Obama Offers Flowers at Hiroshima".
That all, of course, does not mean that the bombings have been forgotten or glossed over.
- 'Convergence of interests' -
Terumi Tanaka, a Nagasaki survivor, said what is most important in Obama's visit is that he express understanding, a sentiment reflected more broadly in Japan ahead of the trip.
"He doesn't have to apologise if he is truly moved, feels remorse and understands what to do to eliminate nuclear weapons," Tanaka told reporters.
What is clear is that the bombings have uniquely bound the two countries.
"The significance of President Obama's visit is that the US, the world's only nation to have used nuclear weapons, and Japan, the word's only nation to have been attacked with nuclear weapons, will express their strong determination to realise a nuclear-free world", a Japanese foreign ministry official told reporters.
In the decades since the war, the countries came to have much in common: Japanese love baseball and Hollywood while Americans have taken to sushi and anime.
But on a higher plane there is "a convergence of interests, a convergence of values, two societies that for the most part acknowledge and see the world through similar lenses", said Brad Glosserman, an expert on Japan-US relations at think tank Pacific Forum CSIS in Honolulu.
- Occasional tensions -
Still, as in most relationships, there are occasional tensions.
The biggest crisis came in 1960 with massive demonstrations against a revision to their mutual security treaty, scuttling a planned visit to Japan by then-president Dwight Eisenhower.
Trade disputes in the 1970s and 1980s sparked ugly rhetoric and imagery in the US depicting a resurgent, unrepentant Japan winning by economic means what it failed to achieve in war.
The eve of Obama's visit is no exception.
An American civilian working at a US military base was arrested last week over the death of a local woman in Okinawa, where many US bases are concentrated.
Abe, who is under pressure to press Obama on the issue on the sidelines of a Group of Seven summit just ahead of the Hiroshima visit, has said he feels "strong outrage" over the case.
Glosserman stressed that the countries are blessed with "dedicated cadres" of politicians and bureaucrats who make things work, especially in times of just such trouble.
"They know how to deal with crises and they have a stake in resolving these in positive ways," he said.