Yuki Kawauchi, the surprise winner of this week's Boston Marathon, said Thursday he plans to quit his full-time job and go pro next spring.

Upon his return to Japan from the United States, Kawauchi said one year from now he will become a full-time marathon runner instead of working for the Saitama Prefectural Government, his current employer, which bars him from accepting sponsorships or appearance fees.

"The No. 1 reason is that I want to compete at the global level," Kawauchi told reporters at Narita airport.

"I haven't improved my personal best time in five years. I need to change my environment."

Kawauchi, who has made three appearances at the world athletics championships, is known as the "citizen runner," as he works 40 hours a week and trains in his downtime, paying his own way instead of competing for a corporate team. His personal best is 2 hours, 8 minutes, 14 seconds clocked in the Seoul international marathon in 2013.

After years of juggling duties and struggling to make ends meet, Kawauchi said he saw the $150,000 prize money he received for winning the Boston Marathon -- his first major title -- as an opportunity to commit fully to the marathon.

"It really helps that my financial worries are gone," he said.

On Monday, the 31-year-old overtook Kenyan defending champion Geoffrey Kirui in the final two miles to win the wet and windy race in 2:15:58. He is the first Japanese runner in 31 years to win the prestigious race.

[Getty/Kyodo]