Qatar-Japan bilateral relations are poised to become stronger after the two countries issued a joint declaration and signed a number of memorandums of understanding (MoUs).
Shinzo Abe toured the city and commercial hub of Sapporo, where Thursday's 6.6-magnitude jolt has left houses tilted and roads cracked.
Shigeru Ishiba, 61, announced his candidacy on Friday for a Liberal Democratic Party presidential election expected on September 20.
The toll from the record rainfall has continued to rise, as rescue workers dig through the debris and find the remains of dozens of people reported missing.
Torrential rains unleashed floods and landslides in western Japan last week, prompting Prime Minister Shinzo Abe to cancel an overseas trip.
Japan's Prime Minister Shinzo Abe on Tuesday welcomed a document signed by North Korea's leader at an unprecedented summit with US President Donald Trump as a "first step" towards denuclearisation.
Japanese Prime Minister Shinzo Abe, his ratings in a slump amid a suspected cronyism scandal and cover-up, apologised again on Sunday for causing anxiety and loss of confidence in his government.