Former Chelsea boss Emma Hayes lost her first match as manager of the United States as Japan won the SheBelieves Cup.
The US were bidding for a record-extending sixth successive title in the annual round-robin invitational tournament.
Japan, who lost against the United States in the quarter-finals at last year's Paris Olympics, earned revenge at Snapdragon Stadium in San Diego, California.
Both nations started the day on six points but Japan had a far superior goal difference and knew a draw would be enough to claim the title.
Yuka Momiki put the visitors in front after just two minutes following a mix-up between US defender Emily Sonnett and goalkeeper Jane Campbell left her with an open goal.
Ally Sentnor latched on to Catarina Macario's pass to equalise soon after but Toko Koga turned in a rebound to seal victory in the second half.
It is the first time Japan have won the competition, with their previous best a runners-up finish in 2023.
Hayes took over the US team in May 2024 and believes her side are "better off as a result of this experience" as they build towards the 2027 World Cup.
"The relationships they [Japan] have in terms of the volume of games they've played together really shows," Hayes said.
"They were a higher level to us throughout."