It’s hard to argue with the sheer enjoyability of the “John Wick” films. In what feels like a short time, Keanu Reeves and stuntman-turned-director Chad Stahelski have built an original franchise that stands apart from the sea of tried-and-true superhero slugfests. It’d be easy to credit Reeves’ titular rogue killer as the main selling point, but the “John Wick” films also benefit from Stahelski’s own keen eye for both high-octane action and rich worldbuilding.

“I’m a huge fan of Chambara films — sword-fighting films, samurai films — from ‘Harakiri’ to ‘Seven Samurai,'” Chad Stahelski told Total Film. “I can literally name off all 26 episodes of ‘Zatoichi,’ plus the TV shows! So, obviously, that’s a huge influence.”

“John Wick: Chapter 4” in particular takes a lot of influence from samurai cinema. You can see it in the casting choices this go-round — from Japanese-British singer-songwriter Rina Sawayama, to seasoned swordfighters like Hiroyuki Sanada. According to Stahelski, the Japanese influence runs even deeper in the upcoming film: “This one has a very Japanese theme to it,” the filmmaker continued. “It’s about a certain code, whether it’s friendship or the art of living. Even though everyone in the movie is a bad guy, there’s a code.”

With so many seasoned martial artists like Donnie Yen and Scott Adkins looking to join the fray, Stahelski had to ask a bit more of his leading man as well. “I just want Keanu to be better as a martial-art stunt performer by this much,” the director said, pinching his fingers to illustrate. “So he learns the nunchucks, he learns the bow and arrow, he learns all these new tools. Keanu did his part. Keanu got a little better as John Wick.” Reeves is obviously a pretty solid performer as is, but it sounds like “Chapter 4” pushed Reeves to go the extra mile.

Stahelski’s and Reeves’ dedication is pretty serious — but with a franchise that’s already four films deep, can we really blame him for wanting to push the envelope that much further?