Japan's former prime minister Yukio Hatoyama bows in front of a memorial stone during his visit to the Seodaemun Prison History Hall in Seoul, South Korea, Aug 12, 2015. [Photo/IC]

In 2013, Hatoyama went to the Memorial Hall of the Victims of the Nanjing Massacre by Japanese Invaders, becoming one of the very small number of Japanese politicians who have visited.

Hatoyama said "as descendants we must apologize to the war victims, for so many innocent lives were deprived by the Japanese troops, and we should directly express our genuine apologies."

As a country who was defeated, Japan should take its responsibilities and hold the right attitude, which means "until the victims say 'it's OK',we should keep apologizing," Hatoyama said. However, such a way of thinking is rare among Japan's politicians, he added.