It's still early, but at this film set in a rented, two-story house in a Tokyo suburb, "adult video" actor Tetsuya Hatanaka is well ahead of schedule.

Out of consideration to the female costars to whom he will shortly be attending upstairs, the veteran of 800 porn flicks has already showered, shaved, clipped his fingernails and brushed his teeth.

And though 31-year-old Hatanaka's performance style is one of understatement -- "I don't do acrobatics" -- he always warms up with some mild stretches so there are no sprains, just in case.

But more than good grooming and his suppleness distinguish this former salaryman from lesser rivals. Neither is it looks, because Hatanaka is nothing if not plain to look at.

Rather, it's his sheer, almost superhuman cool; his ability to stave off the natural imperative and, with Zen-like willpower, persevere through countless technical glitches, retakes and coffee breaks before finally delivering the goods -- what's known in the biz as the "money shot" -- bang on cue.

That's not a gift bestowed on many, and in Japan there are said to be only about 20 male AV stars out of around 200 actors in the field. Masao Tanaka, chief director and producer at AV company Zeus Collection, says that many self-assured Casanovas apply for a gig, "only to fizzle out" in disgrace when actually facing the camera.

Experts say it's impossible to estimate the size of the Japanese AV industry because so many videos get traded underground. Nonetheless, a glance at the shelves of any video shop attests to its enormous scale and scope, and Tanaka says he wouldn't be surprised if it totaled 100 billion yen. But with times tough all around, customers -- typically males between 20 and 40 -- have become more demanding.

Hatanaka is up to the superstud challenge. Quietly rehearsing his lines (yes, there are lines), this guy is a picture of composure itself.

Eventually, it's time for that "lights! camera! action!" moment, with the filming set to start for Zeus Collection's latest 130-minute epic, "Semezuki 'Madoka & Yumie' Wa Suki Desu Ka (How Do You Like Horny 'Madoka & Yumie'?)." I was about to see for myself what the sharp end of this megabusiness is really all about -- and to try to divine what it is that makes people like Hatanaka tick . . . and tick . . . and tick.

My first reaction as the session gets under way is surprise. Despite the occasional wisecrack, it all seems so refined, what with everybody saying, "Would you be so kind as to . . . ?" and "If all are ready, perhaps we could start rolling?"

Eventually, one of Hatanaka's costars, actress Yumie Watanabe, shuffles along in a brown negligee, painted-on microshorts and slippers and salutes the crew. Hatanaka, dressed in a shirt and pants, and Watanabe, who gives her "stage age" as 26, bow deeply and exchange pleasantries.

The script could have been written for Hatanaka, whose boyish looks are a perfect fit for the teenage main character who visits a classmate staying home with a fever, only to fall for his older sister (Watanabe), a nurse.

The first "hot" scene is shot after lunch -- during which the crew neatly place their bento boxes and chopsticks into one garbage bag and PET bottles into another for recycling.

The scene is a fantasy sequence in which Hatanaka, and not his classmate, has become bedridden with fever. Full-figured Nurse Watanabe comes to his aid.

The camera rolls.

"Nurse," moans Hatanaka. "I feel terrible!''

"You're sooo sweaty!" she coos.

The time has come for the actor to prove his mettle.

Watanabe unbuttons Hatanaka's shirt and begins licking his chest. Straightaway it's obvious that Hatanaka isn't the type to "fizzle out." But, with his face now off-camera, his expression blanks as he looks away and distances himself mentally from her ministrations.

With the lens following her every move, Watanabe works her way down to the rim of Hatanaka's slacks, slurping extra-loudly for the benefit of the sound engineer -- who, with earphones wrapped around his head, looks as serene as if he were listening to an aria.

Off come Hatanaka's pants. Then his Hanes briefs. Then . . .

We have a problem: Hatanaka's belt buckle banged on the floor. Will the soundman nix the take? No, it wasn't that loud and they're still rolling.

But other issues crop up as the shoot slowly progresses. Batteries need replacing. The cameraman breaks wind within microphone range. Electric cables accidentally get draped over Hatanaka's face. And when the couple switches positions, a stray elbow or knee painfully connects with Hatanaka's nether region.

The actor, though, seems not to notice, and certainly remains up to his task. By now, it's as if he has transported himself to another cognitive region entirely. He is in a state of subzero ultracool.

Then finally, after so many shouts of "Cut!" by the director that I lose count, the time for the film's climax arrives. Hatanaka emerges from the void and, answering Watanabe's ardent attentions, discharges his duty.

It's a wrap. Hatanaka and Watanabe tidy up and he gives her a little hug.

"Thanks for your cooperation!" he says.

"Your timing was impeccable!" she responds, with a smile.

Indeed, pacing is an essential element of an AV actor's skill. There's big money at stake in this game. With daily production costs anything between 1 million yen to 5 million yen (though most AV films are apparently one-day shoots), and top actors on around 70,000 yen a day, a performer not up to the job, or unable to sustain himself with something like Hatanaka's insouciance, is unlikely to go far.

During a break -- while he prepares for an encounter with the other co-star, Madoka Ma- tsuba -- I try to learn how Hatanaka takes command of his libido. I figure it's not just me who's curious, and that I owe it to my readers to try to crack this corporeal conundrum.

Perhaps he's a high-flying playboy, with a big black book, and he's simply getting paid for doing what he does naturally?

Wrong. Unmarried Hatanaka says his simple lifestyle is no different from when he was clocking in and out at the personal-loan company where he worked before it was bought out and he came back to the AV world. (He said he appeared in some films during his college days, lured -- he says -- as much by an interest in film as by all things iyarashii (nasty). Today he tells his parents he works in "personnel.")

Likewise, there's no harem, no car. His travels have been domestic except for a trip to Walt Disney World in Florida two years back. And his cramped apartment in Shinjuku Ward is "mediocre -- and with a poor view," he says.

Mostly, Hatanaka just works. He reckons to spend 20 days a month in front of the cameras, and he puts what he says is his "30,000 yen per shoot" pay in the bank. "This isn't the kind of job you can do forever," he says, perhaps embarrassed by his own off-set normality.

Fine, but what explains that amazing restraint that so endears him to directors? Does he visualize pretty mountainsides or something?

"No," he answers.

OK. So is it Viagra?

"I never touch the stuff. It places unneeded strain on the body."

Trying to accommodate me, though, Hatanaka does describe watching videos he's appeared in, taking notes on how to improve this or that technique.

But in the end, the real answer -- the passport to his own "floating world," and his ability to visit and revisit ecstasy on cue up to four times a day -- slips out almost unnoticed.

"I relax," he says. "I empty my mind."