Uno injured his ankle after falling on a quadruple Salchow during Wednesday's practice but showed no signs of discomfort in his routine set to 'Gravity' by John Mayer and came away with a season's best score of 104.63 ahead of Saturday's free skate.
The Beijing Olympics bronze medallist was ahead of American Ilia Malinin (18) who also crossed the 100-point barrier with 100.38 while South Korea's Cha Jun-hwan (21) was behind the duo after a solid 99.64.
Earlier, home favourites Miura and Kihara - who topped the short programme with a career-best 80.72 - earned Japan a maiden pairs world title with an overall score of 222.16 after their free skate.
They dethroned Americans Alexa Knierim (31) and Brandon Frazier (30) who took the silver with 217.48 while European champions Sara Conti (22) and Niccolo Macii (27) secured the bronze with 208.08 for Italy's first pairs medal at the worlds.
Miura was in tears after their performance to 'Atlas: Two'/ 'Shared Tenderness' as she fell while executing a throw triple loop but last year's silver medallists had done enough to bag the gold and delight the home fans at the Saitama Super Arena.
"Our practice paid off in the short programme and though I still have regrets in the free skate I'm happy," Miura said.
"The last few weeks we tried to maintain our composure and work on what we need to work on."
The Toronto-based duo have enjoyed a stellar season, winning all three Grand Prix events including the Final in Turin as well last month's Four Continents Championships.
"We're incredibly thrilled about the season we've had, but we never thought we could do it," Kihara said.
"Just before the season, Riku got hurt which brought about some challenges, but they only strengthened our bond. Our trust, our relationship only grew tighter."
The action continues on Friday with the rhythm component of the ice dance followed by the women's free skate.
