You may not realize how much you want to know about sumo until you go behind the scenes by experiencing Erik Shirai’s immersive Sumo: Spirit Weighs Nothing. The documentary, which world-premiered at Venice and is now screening at the 70th edition of the BFI London Film Festival (LFF), starting on Oct. 13, takes audiences inside the notoriously private world of sumo, from the grueling training and the rituals to the pain and sacrifice.

The cinematic film follows a number of wrestlers in different stages of their careers, including a yokozuna, a title denoting the highest rank in professional sumo, over the course of a year. They are Terunofuji Haruo, Hiradoumi Yuki, Yonezawaryu Daiki and Kosei Motomura. One key takeaway is the importance of fighting spirit. Or as a synopsis puts it: “True strength is measured not in flesh, but in the refining of the spirit.”

The doc, for which Shirai and Hiroshi Harahandled cinematography, with Frederick Shanahan as editor, mixes intimate vérité with poetic observation to reveal more about a sport that often seems particularly foreign to those outside of Japan. Presented by ESPN Film, the movie is a Rise Films production, in association with Real Lava and Generation11.

Japanese-American filmmaker Shirai previously took a cinematic deep dive into another Japanese institution in The Birth of Sake. Ahead of the London debut of Sumo: Spirit Weighs Nothing, he talked to THR about why he wanted to take a closer look at sumo and its spiritual dimension, how he got access and what audiences can take away from the doc.

Before you read on, THR can now exclusively premiere a new clip from Sumo: Spirit Weighs Nothing, in which the yokozuna shares just how much his life expectancy is reduced by his decision to dedicate his life and focus to sumo wrestling. He is making big sacrifices to “live boldly.”

For filmmaker Shirai, sumo was always in the background before he decided to explore it on a deeper level. “I would always hear or see it on TV when we’d be making dinner or waiting for dinner,” he recalls. “But it wasn’t really until I became an adult that I became curious about the whole tradition and the culture. I always felt that the top knot [sumo wrestlers wear their hair in] was almost fake. I thought they were wearing a wig. So, it was really interesting to dive into it.”

And he soon realized that there was much to disentangle and explain. “As I got deeper and deeper, making the film, I realized that there are so many misconceptions about sumo,” Shirai tells THR. “I think that partly why I gravitated towards it was because growing up Japanese in America, I felt like there were a lot of misconceptions about Japanese culture and traditions. So I thought this would be a perfect opportunity to realign some of those misconceptions that people in the West often have and feel about Japan.”

Shirai even found that he had misconceptions himself. “The big thing for me was that this idea of strength was so different from the way that I grew up,” he recalls. “The idea of strength, especially in America, is about men pounding their chests and saying, ‘I’m the best. I’m the greatest. I’m the GOAT.’ They are talking about themselves almost in a way to make their opponents fear them. In Japan, and in particular with sumo, strength is completely built differently. There’s humility built into it.”

No wonder then that Shirai puts one of his key takeaways this way: “One of the biggest things I learned from sumo is that a lot of the things that they talk about in terms of strength are things that you can’t see, particularly your resilience, your dedication. Even if you’re small, you’re agile. And there’s this idea that you have to build your spirit, refine the spirit. So, sumo is just like any other craft. It’s a sort of vessel to better understand yourself and to refine your spirit.”

Getting access to sumo stables, wrestlers, their traditions, rituals and thinking and struggles can’t have been easy. “That was the biggest challenge we had,” Shirai shares. “It took three to four years to get that access from the Sumo Association. They are just notoriously secret, and they have had things happen in the past, so they’re very, very cautious and very, very skeptical about letting outsiders in. So we were very fortunate.”

Building the necessary trust was a process that took a lot of time and patience. “There’s no fast-forward button,” the director says. “A lot of times, I would go there with no cameras, and we would just hang out with the sumo wrestlers, watch them train, talk with them.”

And his team took the athletes out to eat. “One of the agreements that we made with one of the stable masters was that we would have to take the whole stable out for yakiniku, grilled meat,” Shirai explains. “We had to take the whole stable out, and basically they closed out and ate out the entire restaurant. It was unbelievable. I remember seeing the receipt from my producer. He had to pick it up, and he’s a tall guy, but he held it up, but it still rolled on the ground. That’s how long the receipt was. But that was a great way to build this relationship with them, and eat and drink with them.”

Sumo: Spirit Weighs Nothing has an immersive and even philosophical or lyrical quality, and that is by design. “I feel that with any film you have to bring out the humanity in it, and the more you can bring that out, the more people can relate and connect,” Shirai tells THR. “That was especially important with sumo. I think everybody thinks it’s a sport made for fat people, but you really quickly understand that getting fat is the biggest challenge in sumo, especially for these young guys, especially if you’re Asian.”

His hope is that the film can change how audiences feel about sumo: “People may think of it as a spectacle with these big guys and this wardrobe, so there’s an opportunity for people, as they watch the film, to realize that these guys are just normal dudes, and there’s a lot about them that I can relate to.”

The yokozuna, for example, is shown in the doc with his wife and kid, and he discusses his diabetes and other health challenges, which may come as a surprise to many viewers. “In Western culture, we don’t want to talk about our vulnerabilities,” notes Shirai. “But because the yokozuna was at the end of his career, I think he really wanted people to understand the dedication and the sacrifices it took to be in sumo, especially for someone that’s been in it for 15 years. So, he talks about giving up parts of his life, giving up his personal life and having physical ailments that will last for the rest of his life. But when you see that, you understand that he’s doing it for something beyond himself. That’s something that I always found very fascinating about sumo. It’s not about the individual. It’s always about the bigger collective and what you can give to it to keep the tradition and culture going.”

Shirai is leaving it to viewers to make up their minds on what they see as key takeaways from Sumo: Spirit Weighs Nothing. “I’m hoping that they will understand more about what it means to be Japanese, because a lot of sumo is about the pride of the Japanese people,” he tells THR. “It’s bigger than yourself, and it’s about keeping this tradition going. It’s been around for 1,500 years, but it feels kind of obsolete in this modern world. There are no giant or jumbo screens for replays. And everything is so primitive, manual and analog. I hope that people can take away that this is a beautiful tradition and culture and how hard it is to continue that in this modern world.”

Shirai is looking to switch things up for his next film, even if the title may, on the surface, sound like a continuation of his look at how challenging eating so much that they gain a lot of weight is for sumo wrestlers. After all, the title of his next movie is How to Feed A Hungry Ghost.

“I’m finishing up another film that is completely different,” Shirai tells THR. “Literally, there’s nothing further from sumo. It’s a story about a Vietnamese chef who goes back to Vietnam after 10 years away and is feeding her hungry ghosts.”

“My last few films have been really dominated by a lot of male collectives and male energies,” he concludes. “I was attracted to that in some ways because it was exotic to me to explore this male energy and these male groups, because I grew up raised by women. So, my next film is specifically following this female journey. It’s a very different film and a very emotional one, and it’s something I’m very proud of.”