"In my experience, I have never had a person who was prepared to drive after travelling halfway around the world," Judge Kevin Phillips said in court today.
After two hours, Uno began to feel drowsy and pulled over for a nap. But the 15-minute sleep was not enough to make a difference.
At 4.30pm, Uno veered onto the gravel strip on the left of the road before coming to his senses and swerving to correct his mistake.
However, the hasty manoeuvre saw him skid into oncoming traffic.
Seeing this, Lumsden man Dave Miller, who was driving with his wife and teenage daughter, took evasive action.
While he steered into the wrong lane, Uno returned to his lane and the collision happened at 80-90kmh, the court heard.
Koyama, who was asleep at the time, suffered broken vertebrae and required surgery.
Those in the other vehicle escaped severe injury but were heavily impacted by the incident.
Miller said the near tragedy also raised "much larger" questions about tourists being allowed to drive without sufficient experience or rest.
"When is the New Zealand Government going to act on the issue of foreign drivers driving on our roads?" he wrote in his statement to the court.
Defence counsel Cate Anderson said her client had originally planned to stay in Queenstown rather than make the long drive immediately, but a flight cancellation had forced a change of plans.
"Dr Uno was devastated by what had occurred," she said.
Judge Phillips struggled to understand how someone so clearly intelligent made such a terrible decision.
The court heard the defendant was an associate professor at the University of Tokyo School of Medicine.
"An educated person should recognise the risk and stop driving," the judge said.
"In New Zealand on holiday, he let himself entirely down, in my view."
He noted an email Uno sent to his lawyer saying if the story of the crash was picked up by Japanese media, he would be forced to resign.
Despite protestations, he granted applications to photograph the defendant and said the man's employment was a matter for his bosses, not for the court.
As well as the reparation ordered to the Miller family, Uno was banned from driving for a year.
