Chainsaw Man chapter 222 has literally just served us with one of the funniest, most stunning moments in the entire series. And finally, for all the decimation, nuclear punches, and state-gobbling swords that Yoru had thrown at Chainsaw Man, she’d got him right where she wanted.
Pochita was defeated, the world was trapped in endless war without death, and victory seemed certain. But then Denji pulled off the most absurd counter imaginable. He hit her with a peace sign and declared he won at rock, paper, scissors.
Yes, really. That's what happened in Chainsaw Man chapter 222.
The Rock, Paper, Scissors Gambit

Here's the thing about Yoru's powers. She can only turn things into weapons if she believes she owns them. And she typically only feels like she owns something after proving her dominance over it. This could be through winning a fight, buying something, or even winning someone's affection. The keyword here is "perception." It doesn't matter what's objectively true. What matters is what Yoru believes to be true.
So when Yoru reached out her hand to transform Denji into a weapon in Chainsaw Man chapter 222, he saw an opening. Her open palm looked like "paper" in rock, paper, scissors. Denji threw up his signature peace sign, which doubles as "scissors." And just like that, he claimed victory in a game Yoru didn't even know they were playing.
The genius part? Yoru is incredibly competitive and takes games seriously. Earlier in the series, she literally used rock, paper, scissors to claim ownership of the Falling Devil and turn her into clothes. Her own logic got turned against her. Because she genuinely perceived herself as having "lost" this impromptu match, she couldn't maintain her sense of ownership over Denji. The transformation failed.
Why This Works Against Yoru

Chainsaw Man chapter 222 reinforces something we've known about Yoru for a while. She's powerful, sure. Country-level powerful, even given that she literally erased entire U.S. states to make swords. But she's also fundamentally flawed in very human ways. She's prideful, competitive, and surprisingly naive about how people think.
Unlike her sisters Makima and the Death Devil, who were always calm and calculating, Yoru gets emotional. She throws tantrums. She gets embarrassed. And most importantly, she takes everything at face value. When someone presents her with a challenge or frames something as a competition, she can't help but engage with it on those terms.
This isn't the first time Denji's failed to become Yoru's weapon, either. Back when Asa was trying to make him fall for her in Chainsaw Man, the transformation didn't work then either. Fans had theories ranging from "hybrids can't become weapons" to "Pochita is protecting him" to "you can't own someone who already belongs to themselves."
That last theory feels especially relevant now. Denji straight up tells Yoru in Chainsaw Man chapter 222 that "I still belong to me." It's one of his most powerful character moments in the entire manga. Throughout the series, Denji has constantly been used, manipulated, and treated like an object by nearly everyone around him. Makima controlled him. Fumiko literally used him as furniture. But now, after everything he's been through, Denji has finally internalized that he's not property. He's a person.
The Birth of Denji Man in Chainsaw Man Chapter 222

What makes Chainsaw Man chapter 222 so special is how it sets up Denji's new transformation. After asserting his autonomy and blocking Yoru's ability, Denji takes control of his own body from Pochita. Usually, it's Pochita protecting Denji. This time, Denji protects Pochita.
The result is "Denji Man," a fusion form combining Pochita's raw devil power with Denji's human intelligence and battle experience. It's a perfect representation of his character growth. He's not just the Chainsaw Man anymore. He's not just a weapon. He's Denji, a person who makes his own choices.
Of course, Denji, being Denji, he immediately brags about his "high school educated genius brain" in Chainsaw Man chapter 222. The boy may have grown, but he's still the same lovable idiot we've followed since chapter one. And honestly? That's what makes this moment work so perfectly.
Conclusion
Yoru failed because she underestimated the power of someone who refuses to be owned. Simple as that.