Kawauchi tries to sleep at least seven and a half hours a night. And he incorporates ultralong runs into his training to build stamina. He has been known to jog the distance of a marathon three times in a week and to run 62 miles, or 100 kilometers, along a river to his home in seven and a half hours.

Will Kawauchi will run faster when he quits his job and becomes a full-time runner next April? Will more training miles leave him hurt more often, and less resilient in recovery? It remains to be seen.

The 2020 Tokyo Olympics are approaching, but ever the contrarian, Kawauchi said he was not interested. He has struggled running in heat and humidity. It would be a waste, he said, to prepare for the brutal conditions expected in August in Tokyo.

“The Olympics aren’t the only destination an athlete should go for,” Kawauchi said.

He has broader ambitions: To run another personal best in the marathon. To win a medal at the 2021 world track and field championships in Eugene, Ore., where the weather figures to be more accommodating. To run as many marathons in as many countries as possible. Unbound by a civil servant’s job, he will be free to go off and see the world as he pleases.

As a boy, Kawauchi loved to thumb through atlases and read train schedules. But when he began to run, his world turned inward. He said he thought of little but trying to follow his coach’s plan perfectly. Now he makes his own plan, longs to try new things, see new places.

“He’s a clever runner,” said Sugita, the chief scientist of Japan’s track and field federation. “He thinks for himself.”