Japan earned promotion to World Group II in the Fed Cup after ace Ayumi Morita coasted to victory for an insurmountable 3-0 lead over Argentina in a play-off tie on Sunday.
After the hosts took a 2-0 lead on Saturday, the 23-year-old Morita whipped Aranza Salut, who replaced the out-of-form Maria Irigoyen, 6-2, 6-1 in the best-of-five contest.
On Saturday on the indoor hard court in the city of Kobe, up-and-coming Misaki Doi, who reached the third round at Wimbledon at her first attempt, whitewashed Irigoyen 6-0, 6-0 in the opener to give Japan the perfect start.
Morita, ranked 47th in the world, followed her with a solid 6-2, 6-3 victory over Mailen Auroux in the second singles.
Japan are promoted along with Belarus, Slovenia and Switzerland.
The play-off was originally scheduled for April but the earthquake and tsunami and ensuing nuclear emergency in northern Japan forced its postponement.