Miyu Kato and Makoto Ninomiya beat Britain's Johanna Konta and Heather Watson in doubles on Sunday to earn Japan promotion back to Fed Cup World Group 2.
With their Fed Cup playoff tied at 2-2, Kato and Ninomiya came from behind to win the fifth and deciding match 3-6, 6-3, 6-3 at Bourbon Bean Dome.
Earlier in the day, Naomi Osaka lost her reverse singles match to Konta 6-3, 6-3. However, Kurumi Nara kept Japan's hopes alive by beating Watson 7-6 (9-7), 6-4 in the other reverse singles match.
With the victory, Japan will now return to the eight-nation World Group 2 next year for the first time since 2014. It is from among that eight-nation group that four nations qualify to play in the final championship round.
"(Kato and I) have been preparing so we can win our match when promotion is on the line. I'm really glad we were able to win for the team," Ninomiya said.
Last-minute changes sent Konta and Watson back on court after each had played a singles match earlier in the day.
Ninomiya and Kato dropped the first set, but picked up momentum as the match progressed and swept to a 5-0 lead to put the second set out of reach.
The pairs were tied 3-3 in the decisive set before Japan broke to take the lead and held on for the win.
"We were playing well from the beginning. We got a bit stiff but pulled ourselves together in the second set," Kato said. "We worked together and played aggressively, and that led to us winning our rubber."
