In Osaka, Daichi Kamada scored after 15 minutes to set Japan, preparing for an eighth consecutive World Cup, on the way to a 6-0 victory.
Takefusa Kubo added a second five minutes later and Kamada extended the lead just before the break. Soon after the restart, Ryoya Morishita and Shuto Machino piled on and Mao Hosoya made it six.
South Korea, already qualified for an 11th straight World Cup, sealed top spot in Group B after beating Kuwait 4-0 to complete an unbeaten campaign.
Jeon Jin-woo scored after 33 minutes at Seoul World Cup Stadium and Lee Kang-in added a second soon after the restart. Oh Hyeon-gyu and Lee Jae-sung also got on the scoresheet.
In Asia's third round of qualification, the top two from each of the three groups of six progress automatically to the World Cup. Jordan, Uzbekistan, Iran, Japan and South Korea have qualified for the expanded 48-team tournament in the United States, Canada and Mexico.
Australia, the only team to beat Japan in qualifying, later joined them with an impressive 2-1 win in Saudi Arabia.
The Saudis will join the other five teams that finished third and fourth in a fourth qualifying stage with Asia having two remaining automatic places.Â
UAE, Qatar, Iraq and Indonesia already had spots booked and Oman claimed the last with a 97th-minute equaliser against Palestine in neutral Jordan, despite being down to ten men, edging out their putative hosts.
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