Obama and his fellow world leaders from the club of rich democracies are gathering for a meeting where much energy will be spent discussing the lacklustre state of the global economy.
But it will be Obama's trip to Hiroshima as the only sitting president to visit the site of the world's first nuclear attack that is likely to dominate the headlines this week.
"Our visit to Hiroshima will honour all those who were lost in World War II and reaffirm our shared vision of a world without nuclear weapons," Obama said at a joint press conference with Japanese Prime Minister Shinzo Abe.
The leaders of Britain, France, Germany, Italy and Canada were also making their way to Ise-Shima, a mountainous and sparsely populated area 300 kilometres (200 miles) southwest of Tokyo, whose mainly elderly residents rely chiefly on tourism and cultured pearls.
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Security was tight across the region, with thousands of extra police drafted in to patrol train stations and ferry terminals, and to direct traffic on the usually quiet roads during the two-day meeting.
Tokyo said it was taking no chances in the wake of terror attacks that struck Paris and Brussels in recent months.
Authorities said they will be keeping a close eye on so-called "soft targets" such as theatres and stadiums.
However, unlike in many other rich democracies, protests were unlikely to cause much of a security headache.
One left-wing demonstration organised for today morning -- and focused mostly on Japan's domestic politics -- attracted just a handful of largely elderly protesters.
Britain's David Cameron, whose country's referendum next month on continued membership of the European Union was likely to figure prominently on the summit agenda, arrived late afternoon at the main international airport near Nagoya.