The average Japanese today are more akin to us then their nationalistic ancestors of just 50 years ago. They still have a very structured society, of course. But, many of the former trappings of nationalism that hung around after the war are gone or no longer of interest. When I arrived in Japan in the seventies, martial arts schools of all types were popular. The training was hard and the discipline taught was very militaristic. Samurai or Yakuza movies were popular. The lone warrior fighting injustice and dying for what was right. Yakuza popularized as epitome of the Nationalistic ideal. They were not liked but feared. Now the Yakuza are seen for what they always were, criminals to be despised This was because the generation that was running the country and the Yakuza had been born and raised on nationalism prior to WWII. On a recent visit, the change was very noticeable. The WWII generation is disappearing and are far less influential. The younger generations moved on from the nationalism. They accept foreigners to live in Japan now and have cracked down on organized crime. Although it seems the Triads are moving in. The nationalism, it is still there below the surface, but then that is true about us as well.
If the emperor was still not believed to be a descendant of Amaterasu (the sun goddess), then organizations like Nippon Kaigi (linked to the State Association of Shinto Shrines) would not exist. Like you said about nationalism, beliefs such as this are just under the surface.