Well, not only do they not feel guilty about WWII, they've gone so far as to establish a special holiday in honor of the Emperor who led them through that war. Colin Liddell explains:
April 28, 2013 Colin Liddell
Today (April 29th) is Showa Day here in Japan. This is a national holiday, held in honour of the Emperor Hirohito. Showa is his death name and the name of the period defined by his reign (1926-89), a period when Japan made two distinct grabs at world domination and came reasonably close in both cases before the constrictions of being a relatively small island nation kicked in.
Of the three Axis heads of state – Hitler, Mussolini, and Hirohito – only Hirohito’s birthday is honoured in this way.
Showa Day is also the only national holiday in Japan commemorating an individual. The incumbent emperor’s birthday is also a national holiday but that is more a celebration than a commemoration. The previous emperor Taisho (1912 – 1926) is not commemorated at all, and even the Emperor Meiji (1852 – 1912), whose long reign saw the modernization of Japan and its rise to great power status, does not have a day named after him. Since 1948, his birthday (November 3rd) was taken over to celebrate something called “National Culture Day.”
This process of replacing a symbol of nationalism with an innocuous generic theme was actually reversed in the case of Showa Day. After Hirohito’s death in 1989, his birthday was initially celebrated as "Greenery Day," but in 2005, during the premiership of Junichiro Koizumi, Greenery Day was moved to another date and the 29th of April was renamed to commemorate the Emperor whose reign oversaw the invasion of China, the attack on Pearl Harbor, the Pacific War, and the rebuilding of Japan.
If we make a comparison with America, the only equivalent in the calendar of holidays is Martin Luther King Day. Like Hirohito he is the only individual commemorated with a national holiday in his name. (Keep reading HERE.)