Akihito, 85, took the throne in 1989 and devoted his career to making amends for a war fought in his father's name, while bringing the aloof monarchy closer to the people.
With his commoner-born wife, Empress Michiko, he reached out to the people, especially those who faced handicaps and discrimination, as well as those hit by disasters, illuminating the hardships of people often overlooked by society.
Akihito was the first emperor to marry a commoner, one of many changes he brought to the palace. The couple also chose to raise their three children instead of relying on palace staff, and decided to be cremated upon their deaths in a smaller tomb side by side, also a tradition-breaking step.
"You can say that over the past three decades, Akihito has been Japan's chief emissary of reconciliation," said Jeff Kingston, Asian studies director at Temple University, Japan Campus. "In bringing Japan close to the people, he has also acted as consoler in chief ... and he has also been a strong advocate of the vulnerable and the marginalized in the Japanese society."
"I think the people really warmed to him and felt that the monarchy was relevant to their lives because of these efforts by Akihito. He invented these roles and was really remarkable that he was able to stretch these envelopes that far" despite the tight controls by the Imperial Household Agency, Kingston said.
Akihito's efforts won him widespread respect, and recent media surveys have shown public support for the imperial family at 80 percent, the highest ever for the institution.
Such respect did not come overnight. Akihito grew up during World War II and was 11 when his father Hirohito announced the end of the war on radio. Akihito embraced his role as peacemaker and often represented his father on reconciliatory missions as young crown prince, decades before he became the emperor himself.
He is the first emperor in Japan's modern history whose era did not have a war. Though he has avoided outright apologies, he has stepped up his expressions of regret in carefully scripted statements on the war.
Akihito visited China in 1992 and offered what was considered the strongest expression of regret over the war. He has also visited the Philippines and other Pacific islands conquered by Japan that were devastated in fierce fighting as the U.S.-led allies took them back.
Akihito will be known as the emperor emeritus and will no longer have official duties after he abdicates. He won't even attend his son's succession rituals so as not to interfere with the serving emperor.
Akihito is expected to enjoy his retirement, going to museums and concerts, or spending time on his goby research at a seaside Imperial villa. Akihito and Michiko will move to a temporary royal residence before eventually switching places with Naruhito.