Denji is facing a new menace as Season 1 of Chainsaw Man progresses. He had no trouble using his powers to slay devils like the Bat at first, but that changed when his Public Safety Unit was assaulted by unknown intruders. It was particularly violent in eliminating many of Denji's comrades, however Makima and the tenacious Kobeni survived.
However, as the ruckus unravels, Denji finds himself face-to-face with his fiercest opponent ever. His wild side, admittedly, is ready for the challenge and hungry for a fresh violent experience to replenish and grow. But as the struggle develops, Denji gets knocked down brutally, getting his own version of Naruto's Sasuke in the process.
The Samurai Sword is Denji's Very Own Sasuke
Denji harnesses the power of his devil, Pochita, the same way Naruto did with Kurama, the Nine Tails Demon Fox. However, the Chainsaw Man protagonist's mission is more violent as he goes about cleaning up Japan, becoming this weapon of mass destruction. Coincidentally, he meets a man in a diner who taunts him about his work. The guy then shoots up Denji's team, causing the teen to transform. However, when Hayakawa's Fox Devil eats the guy, he's revealed to be the Samurai Sword, cutting his way out.
He's visually like Denji, only with swords in his body rather than chainsaws. The thing is, he's stronger, faster and knows more about military tactics. It's why he disposes of Denji's posse and ends up slicing Denji in half. It stuns fans as everyone assumed the protagonist was the most badass devil-hybrid, but Samurai Sword (or as the manga calls him, Katana Man) takes the hero down with ease. It nods to the earlier days when Sasuke and Naruto were teens, where Sasuke, brooding and sulking like this tyrant, kept trying to kill the fan-favorite hero, affirming he was more powerful at that stage.
Chainsaw Man's Sasuke has a personal beef as well.
Now, Sasuke hated Naruto and Konoha because of how his Uchiha Clan was wiped out by his own older brother. Itachi did this to save the Hidden Leaf, because their tribe was going to destroy it in an act of sedition and terrorism. Still, Sasuke didn't care -- he just wanted revenge as he'd lost everything he had that night, including Itachi. It's why, as the sole survivor, Sasuke marked Itachi and the village for death.
Chainsaw Man's Samurai Sword has a similar emotional vendetta, reaffirming to Denji how the Chainsaw Man took his only family away. It turns out, the Yakuza boss who enslaved Denji as a kid and got him to work off his dead father's debt was the Sword's grandfather. Denji ended up killing the old man after the Yakuza got corrupted by a devil at the start of the series and tried to backstab him, so the Sword wants to exact vengeance.
Ultimately, he doesn't care about any reasoning -- he just wants the object of his wrath dead. It's akin to how Sasuke marked Naruto as the symbol of all his childhood pain, with the Sword wanting Denji's heart for his mysterious employers. Thankfully, Kobeni saves Denji, but after the maiming, she knows they've bitten off more than they can chew against someone far more powerful than their biggest gun.