Mori revealed last month that he had been successfully treated for cancer, and with Japan set to host the Rugby World Cup for the first time in 2019, he told Kyodo News "it isn't good" that he continues to take responsibility for two major sporting events.

"I shouldn't be pushing myself too much physically," said Mori, who has served as President of the JRFU since 2005.

"I've been thinking for a while that I will have to quit some time.

"I want to slow down the pace."

Mori, one of Japan's most unpopular ever Prime Ministers, had been a controversial appointment in January 2013 to head Tokyo 2020.

At the time he joked: "I am destined to live five or six more years if I am lucky.

"This will be my one last service to the country."

The 77-year-old told his fellow JRFU members of his decision at the end of last year, having been in the Presidential hot seat for five terms.

Tadashi Okamura, finance chairman of the 2019 Rugby World Cup and former President of the Japan Chamber of Commerce and Industry, is reported to be a candidate to succeed Mori.

“[The new President] will be a person who from the standpoint of organising a World Cup is well versed in a wide area, including politics, business, bureaucracy and sports,” added the incumbent.

In a busy period for Japanese rugby, the JRFU is also preparing to take its place in the Southern Hemisphere’s Super Rugby competition.

South Africa, New Zealand and Australia Rugby (SANZAR) confirmed in November that Super Rugby would be expanded to 18 teams from 2016, welcoming the participation from the JRFU and the Union Argentina de Rugby. 

Related stories
March 2015: 

February 2014: Tokyo 2020 President claims he does not speak English because it is the "enemy's language"

February 2014: Tokyo 2020 officials not too old, claims executive director

January 2014: Tokyo 2020 unveils Organising Committee amid fears over ages of top officials

July 2009: England and Japan to host 2015 and 2019 Rugby World Cup