WARNING: Some links contain pictures of explicit, NSFW content.

World champion masturbator Masanobu Sato isn't shy.

He's pleasured himself in front of crowds at San Francisco's annual Masturbate-a-thon, and has even talked to the press about his handy, award-winning techniques.

But now the Japanese sex toy representative and his girlfriend are opening up about one of Sato's favorite pastimes for an online series on masturbation produced by Metropolis. (Watch video above.)

The two-time champion begins masturbating for two hours every morning as his girlfriend goes about her daily routine.

But the woman isn't phased by Sato's actions, and sometimes she even helps out by timing his performances.

"He puts a lot of effort in it, and I just have my own hobbies," she explains in the video clip.

In 2009, Sato broke his own record by masturbating for an impressive 9 hours and 58 minutes at the Masturbate-a-thon, the San Francisco Weekly reports. His previous record was 9 hours and 33 minutes.

But self-gratification isn't all fun and games. Apparently, there's some actual training involved when preparing to go the distance.

"I swam twice a week and gained about 5 kgs in muscle," he told the San Francisco Weekly in an email. "That helped me a lot, too, in terms of stamina."

The Masturbate-a-thon is an annual affair sponsored by the Center for Sex and Culture in San Francisco, where events are held in a place appropriately titled the "masturbatorium."

If a man is taking part in a competition, he must stay aroused without ejaculating for as long as possible, a 2010 article in the San Fransisco Weekly explains. At times, the event attracts more males than females, which can be a turn off for some participants.

For more on Sato's story, watch the video report by Metropolis embedded above.