Celebrated abroad for films that mash up everything from extreme sex and gore to Christian imagery and classical music, Sion Sono has emerged as one of the most distinctive directors in Japanese cinema this century.

His breakthrough came in 2001 with "Suicide Club," in which 54 teenage girls kill themselves en masse, and he has since directed films such as "Love Exposure" (2008),a four-hour tour de force whose hero is an "upskirt" photographer, and "Himizu" (2011), a near-future dystopian drama themed on that year's nuclear disaster.

At home, Sono's biggest hit is "Shinjuku Swan," a 2015 comic thriller set in the disreputable world of "scouts" — guys who roam the streets of Shinjuku and other entertainment districts recruiting women for the sex trade. Based on a best-selling manga series by Ken Wakui that has generated 38 paperback volumes, "Shinjuku Swan" earned a solid ¥1.33 billion at the box office.

Now Sono and producer Mataichiro Yamamoto, whose credits include the 1985 Paul Schrader drama "Mishima" and the 2009 Takashi Miike actioner "Crows Zero II," have teamed up again for the sequel, "Shinjuku Swan II," which opens on Jan. 21.

This time our hero, the good-hearted and two-fisted Tatsuhiko (Go Ayano), is swept up in a turf war between his scout team, Burst, whose boss has decided to expand into Yokohama, and a Yokohama team called Wizard, which is led by the violently explosive Taki (Tadanobu Asano). As the two teams clash — and Wizard mounts a counter-offensive on Burst's home ground — the action and intrigue escalate, with powerful yakuza bosses upping the life-or-death ante.

Fans of both the manga and the first film will find many of their favorite characters in the sequel (though viewers new to the story may initially feel lost in the on-screen crowd), while the action scenes, supervised by the Hong Kong-trained Kenji Tanigaki, are larger in scale and impact. Sono has an obvious affinity for the material — his 1995 "Bad Film" and 2014 "Tokyo Tribe" also feature big pitched battles between rival gangs — but his signature style and concerns are harder to spot.

Speaking to The Japan Times just before the film's gala premiere at Roppongi Hills Toho Cinemas, Yamamoto says that he'd always planned to make a sequel.

"With a big manga like that you can't tell the whole story in just one film," he says. "But it depended on whether the fans found the first film interesting. If a lot of fans didn't come to see it, financially we couldn't justify making the second installment."

With a sly glance in Yamamoto's direction, Sono says the first film's success didn't surprise him in the slightest.

"Since Yamamoto was the producer in charge, I rather expected it," the director says.

Known as a creative producer with intimate knowledge of the business — and in contrast to the salarymen who fill the producer ranks on most commercial films here — Yamamoto describes himself as "the type who says nothing to the director on the set, though we spoke in detail before production began."

"I've seen a number of Sono's films and have become a fan," he adds. "He doesn't make films that are hard to understand, but he is a director whose work has been extremely edgy and very much his own. I had high expectations that we could add that edge to this film as well."

"I wanted to make 'Shinjuku Swan,' not a 'Sion Sono film,' " Sono counters, a shade testily. "I'm tired of making a 'Sion Sono film' every time. I didn't think it would be interesting to make this film my own."

Yamamoto responds with a laugh that implies "Sono's being Sono."

"I just shot it according to the script," Sono continues. "For me that sort of thing is new and fresh and not as boring as usual."

However, Sono adds that he also did research, including interviews with actual Shinjuku scouts.

"They make a lot of money," he says. "The top earners can make ¥8 million a month. I thought that was amazing, but it's also tough."

Further diluting the film's "Sono quotient" are the aforementioned action scenes handled by Tanigaki, described by Yamamoto as an action director "with a great reputation." His work includes the 2002 vampire sequel "Blade II," Peter Chen's 2011 film "Dragon" and more than 30 other titles.

"The fact he has been so active in Hong Kong is a testament to his ability. I gave him his freedom and let him do what he wanted," Yamamoto says before admitting that he also told Tanigaki that the action shouldn't overwhelm the drama.

Sono describes the action scenes in "Shinjuku Swan II" as "places where I could be the most free with my ideas — the action wasn't described in detail in the script."

He mentions one spectacular scene where giant billboards advertising Shinjuku host clubs come tumbling down on several scouts, sending them fleeing.

"That was my idea," he says. "I would sometimes bring ideas for adding a bit of color to the scene to Tanigaki and his team, but I left the technique of how to do it up to him."

Another challenge was boiling down the script, which Yamamoto had written under the pen name Rikiya Mizushima.

"If we had shot everything (in the script) the movie would have been four hours long," Yamamoto says. "The shoot would have dragged on too long and the director's schedule wouldn't allow it."

Instead, Yamamoto had the running time edited down to 133 minutes.

"That made the pace extremely quick," he says. "You'll be hard-pressed to find any boring moments in the film."

The fast pace, he believes, will improve the movie's overseas prospects compared to its predecessor, which received mixed reviews and a muted reception abroad.

"The previous one had some sentimental scenes that appealed to the Japanese, but Americans didn't really care," Yamamoto says. "The pace (of the new film) will be more appealing to them."

For Sono, however, the casting of Ayano as the lead in both films is central to their appeal. Represented by Yamamoto's agency Tristone Entertaiment, Ayano has shot to stardom in the current decade with lead roles in Mipo Oh's 2014 award-winning drama "The Light Shines Only There" and Kazuya Shiraishi's 2016 cop thriller "Twisted Justice."

"It's really Ayano's movie," Sono says. "In fact, I got on board (the first film) because Ayano was in it. If they had cast someone I didn't know as the lead (in the sequel), I would have probably dropped out in the middle. It was a really tough shoot."

In Ayano, Sono saw hints of Yujiro Ishihara, an action star for the Nikkatsu studio in the 1950s and '60s. Ayano's Tatsuhiko has something of the young Ishihara's cockiness and swagger, as well as a good-natured naivete all his own.

"I wanted to make an action drama with a cool actor, something like the films of Ishihara," he says. "In that sense it's completely different from anything I've done before. I'm glad I did."

Sono then switches to English: "I'm really satisfied."

"Shinjuku Swan II" opens in cinemas nationwide on Jan. 21. For more details, visit www.ss-2.jp.