Dame Sarah Storey equalled Great Britain's record for Paralympic gold medals by claiming the 16th of her exceptional career with victory in the women's C5 time trial.
Cyclist Storey emulated the achievement of former swimmer Mike Kenny in a time of 36:08.90 on the Fuji International Speedway circuit.
Fellow GB rider Crystal Lane-Wright snatched silver in 37:40.89, with Germany's Kerstin Brachtendorf taking bronze.
While Storey must wait until Thursday's C4-5 road race for a chance to fully surpass 76-year-old Kenny, she is now already more successful owing to a total haul of 27 medals to his 18.
"I never set out on this journey to be Britain's greatest Paralympian, but to match the best man and to have more other medals is just a dream come true - well, it is almost a dream that was not one," she said.
"The closer we have got to Tokyo, the more it has been like: This is a possibility. It really could happen. You just don't know.
"I am just so chuffed. I have been preparing for this for such a long time. It is such a sweet feeling.
"Sweet 16!! Can I be 16 again?!"
The last of Kenny's 16 titles and two silvers came in Seoul in 1988, four years before Storey kicked off her own Paralympic career as a 14-year-old swimmer in Barcelona.
She won five golds in the pool across four Games before a seamless transition to the bike ahead of Beijing 2008, which has brought even greater rewards.
The 43-year-old travelled to the Far East needing three more titles from as many events to stand alone as Britain's most successful Paralympian.
In the foothills of Japan's highest peak, Mount Fuji - approximately 68 miles south-west of the host city - she ticked the second of those boxes in dominant style, having kicked off her quest with a crushing victory over compatriot Lane-Wright in taking GB's maiden medal of the rescheduled Games with last week's triumph in the C5 3000m individual pursuit.
Storey was up before her alarm on Tuesday morning - just after 5.30am local time - and was last to depart in the second race of a packed schedule.
On a circuit where British Formula One driver James Hunt clinched the 1976 World Championship during his battles with great rival Niki Lauda, the mother-of-two was at times forced to dodge riders in the men's race as she relentlessly powered on in overcast conditions.
Crossing the finish line prompted a punch of the air, securing a time trial title at a fourth successive Games to set up a chance of further enhancing her place in the history books later in the week.
"That is something that may happen in the future - it may happen on Thursday," she said of reaching 17 golds.
"Who knows in a road race?
"There is no foregone conclusion in any race, but especially not in a road race."
First gold for Watson
Paralympic Games debutant Ben Watson claimed GB's second gold of the day, just over two months after a high-speed crash into a house while competing in Portugal.
The 32-year-old, who was working as a chartered surveyor at the time of Rio 2016 and weighed around 14 stone due to a party lifestyle, finished the men's C3 time trial in 35:00.82.
"The worst bit about the house was there was a chain-link fence about a metre and half down the road and if I'd hit that that would probably mean I wasn't here because it was about a 15-foot drop onto concrete," he said.
"Fortunately, the house was fine; I wasn't. I cut and lacerated all my arms, all my shoulders and back, the inside of my leg and my groin.
"But I managed to get up and to now be Paralympic champion it's an amazing feeling and one I honestly didn't think I'd get. It's mental."
Watson finished ahead of German duo Steffen Warias and Matthias Schindler, with team-mates Fin Graham and Jaco Van Gass fourth and sixth respectively.
Lora Fachie won silver in the women's B time trial in 48:32.06, while dual-sport athlete George Peasgood crossed the line in 46:08.93 to add C4 time trial bronze to the PTS5 triathlon silver he picked up on Sunday.
Peasgood's medal was the 1,000th won by ParalympicGB and TeamGB combined since National Lottery funding began in 1997.