Central Japan Railway said the 29-year-old acknowledged that he operated the high speed train in that position for 10 seconds on Tuesday.
“He told the company that he had tired feet,” a spokesman for the operator said, also telling AFP that there was never any danger to the 320 passengers aboard the Tokyo-to-Osaka train.
“Shinkansen are equipped with an automatic control system that manages speed and the distance between trains,” the spokesman said.
Central Japan Railway, however, in a statement called the behaviour “extremely inappropriate” and vowed a “strict” response, suggesting the driver would be punished.
Responses on Twitter were mixed. “I wonder if it was necessary to expose the photo on the internet,” one Twitter user said, while others criticised him, with one saying he “should know he’s responsible for passengers’ lives”.
Japan’s ultra-efficient shinkansen network was inaugurated in 1964 as Tokyo readied to host the Olympic Games and has become a symbol of the country’s technological prowess and efficiency.
It has an unparalleled safety record, with no crashes or fatalities due to mechanical reasons in its half-century of service.
Last year, however, a man set himself ablaze on board a moving bullet train, killing himself and a woman in an unprecedented incident.