With the mercury rising to 17 degrees, March 8 was unusually warm for the time of year in Tokyo. Spring was in the air. At Tokyo Dome that evening, though, it was distinctly subtropical as 20,000 people broke out into a midsummer-style sweat.

What set the crowd on fire was not a baseball game or a rock concert. It was a carnival night for "Matsuken Samba 2" -- the hottest of the sizzling samba performances that have lately been winning devoted fans among both the young and not so young.

On a date chosen because "three" and "eight" can be pronounced in Japanese to sound similar to the word "samba," Matsuken Samba 2, performed by the popular, 51-year-old TV samurai actor Ken Matsudaira, is a fun, upbeat spectacle of catchy music and basic samba steps. It's not your Rio carnival, with bikinis, boas and bare flesh by the acre . . . but it has an electricity all its own.

With his topknot hairstyle and heavy stage makeup, Matsudaira -- Matsuken to his legions of fans -- appears on stage resplendent in a glittering kimono, golden tabi socks and slippers. In this startling guise he starts to wiggle his hips and dance as he sings what translates from the vernacular as:

"Play the bongo / Roll the samba / Dance the southern carnival / Everyone is having a ball / Their shining sweat flies.''

Then, behind this most unlikely looking samurai, long lines of men and women troop onto the stage, each in gaudy gold, blue and pink kimono sporting 18th-century hairdos. With gleaming smiles, this chorus of gyrating delight answers their leader with the lines:

"Ole! Ole! Matsuken Samba! / Ole! Ole! Matsuken Samba! / Come on, fall in love, amigo / Dance with me, senorita / Let's dance through the night / Samba viva Samba! Matsuken Samba, ole!''

Whether or not true samba dancers would recognize this as the genuine article is neither here nor there to the enraptured, ecstatic audience. What counts is simply the uplifting melody, the repetition of the word "samba" and the sense of joy and fun that whips one and all into a hip-jiggling frenzy.

"I love it because it's fun and bright and everybody can join in," said Yukari Fukuno, a 46-year-old from Chiba Prefecture who came with two coworkers from a welfare center. Fukuno said she first danced Matsuken Samba 2 a few months ago at a monthly "singing opportunity" for her center's users. At once she was hooked. Since then, she and her friends -- along with many thousands who flocked to dance with Matsuken that day -- have kitted themselves out in costumes like those on stage.

Although Matsuken Samba 2 really took off just last summer with its release by a major record label, Matsudaira has been shimmying his stuff for a decade, though not always in quite so flamboyant a way. As the title implies, there was a "Matsuken Samba 1" -- as well as a "Matsuken Mambo" and other Matsuken songs and dances -- that featured in previous Matsudaira stage shows.

Typically, these shows begin with Matsudaira performing excerpts from his famous TV series "Abarenbo Shogun (The Swashbuckler Shogun)" that ran for two decades until 2003. In that show, the handsome actor played the 8th Tokugawa Shogun Yoshimune, who dons a disguise and goes into town to fix average people's problems. In the second half of his stage extravaganzas, Matsudaira treats his audiences to a song-and-dance show, though until last year he was the only one costumed in a glittering kimono.

All that changed when Geneon Entertainment Inc. issued "Matsuken Samba 2" in July. Before then, as Shinji Kawaguchi of Geneon explained, Matsudaira's samba-show fans were overwhelmingly women over 40 years old, complemented by a cult following from the underground music scene, where many discriminating DJs dig its "cool" kudos.

"Unlike most songs that we start to promote from scratch, there were already these core fans awaiting its release," Kawaguchi said. "So from the beginning we got favorable coverage in the media."

It's coverage that has certainly paid off, as more than 500,000 CDs have been sold in Japan since July, and they continue to sell like hot cakes -- both as the original version and remixes by musicians including Yasuharu Konishi from the legendary pop group Pizzicato Five.

Then there's the how-to-dance DVD, which has sold more than 150,000 copies since its mid-December release. Matsuken's exposure on NHK's traditional yearend singathon "Kohaku Utagassen" also gave a big boost to sales, Kawaguchi said.

The upshot of all this is a fan base about as wide as any artist could wish for. Not only are small children around the country performing Matsuken Samba 2 at their kindergartens, but countless yearend office parties also got into the samba groove, and even a group of high school students at Tokyo Dome said that they are planning a performance to congratulate the seniors graduating at the end of this month.

Joining Matsudaira on stage at the March 8 show at Tokyo Dome were two groups who won a competition to take part in the all-singing, all-dancing spectacular. One of these was a group of medical staff from the Research Hospital of the Institute of Medical Science of the University of Tokyo.

"They performed as part of a Christmas event to amuse the patients, but I didn't know that they had entered this contest," said Aikichi Iwamoto, director of the hospital who came to cheer on his staff's act. "I don't think there was ever a time when our staff became so united," he added with a laugh as he returned to shake his body along with the throng.

So how does Matsudaira himself feel about his samba stardom? "I never thought I'd come this far. I wasn't sure if people would really gather here tonight and I'm grateful," the humble actor said after the night's show during which he danced and sang the samba four times, and also crooned another 10 of his own songs.

"I guess people like the catchy song and dance. It's nice to see such a happy movement in these gloomy times," he added -- while being far too polite himself to mention that his nationwide tour has just begun. Ole!