Sakamoto was in tears in the kiss-and-cry recalling memories of dropping to fifth from second at the same venue in 2019, but it was only joy and relief as her overall score of 224.61 flashed on the Saitama Super Arena screen.
Victory was achieved thanks to breathtaking run to Elastic Heart by Sia during which the Beijing Olympics bronze medallist executed a double axel and a triple Lutz before impressing the technical panel with her combination jumps.
She also became the first women to capture successive world championships titles since Evgenia Medvedeva (23) in 2016-17.
"I felt a lot of support here," Sakamoto, who led the field with a short programme score of 79.24, told the rapturous crowd.
"Initially it was a lot of anxiety and tension, but I was able to turn that into a strength, so thanks for that."
South Korea's Lee Hae-In (17) won silver with a score of 220.94 while Loena Hendrickx (23) of Belgium took bronze with 210.42.
Earlier, Americans Chock and Bates scored 91.94 in the rhythm dance segment of the ice dance competition as they chase a first world title with Olympic and world champions Gabriella Papadakis (27) and Guillaume Cizeron (28) not competing this season.
"We're thrilled with the score," Bates, who bagged the Four Continents title with Chock last month, said of the pair's new personal best that they achieved while performing to a "Let's Dance" remix.
"It's always nice when you come off the ice feeling like you've skated well and then you see a score that reflects the feeling that you had inside."
Italy's Charlene Guignard (33) and Marco Fabbri (35) stayed in the hunt behind the 2022 bronze medallists as the European champions scored 88.21. Piper Gilles (31) and Paul Poirier (31) of Canada were third with 87.34.
The Canadians, winners of the Grand Prix Final, were back on the ice after a break due to Gilles having an appendectomy.
The ice dance continues with the free dance component on Saturday, ahead of the men's free skate where Japan's Shoma Uno will look to defend his title after taking a healthy lead in the short programme.
