He's in One Piece, but he's also part of the Phantom Troupe.

As the giant ship named Black Whale crossed the endless sea, what awaited them was the gatekeeper and the dark continent behind him... What? You're telling me the gatekeeper is Gol D. Roger? The dark continent is full of purple fruits that can awaken Nen abilities if eaten? What... Hell Rattlesnake is Kaido? Gas-like life form A is Crocodile? Nurturing Beast Papp is Big Mom? Iron Body is actually "Firm"? Finger Gun is actually "Hair"? Paper Drawing is actually "Flow"? Observation Haki is actually "Circle"?! Master, I understand! After the Black Whale survived the Great Battle Royale, some died, some escaped, and Kuroro, who rewrote the ending and ultimately won, led a new Phantom Troupe, riding the Black Whale, and set sail! The New World? Isn't this the New World? What kind of extremely evil people? Are the spiders evil enough?! ...A modern college student named Kuro, who knows the whole story, transmigrates into Kuroro's body. Good news: We've traveled through time! The entire Phantom Troupe is alive, and the Thief's Ultimate skill has been upgraded. Bad news: We've entered the wrong universe; this is One Piece. No problem, since we're here, let's plunder to the fullest! The [Thief's Ultimate] manual slowly unfolds, revealing thousands of Devil Fruit abilities stolen by Clow Hand. He gazes indifferently at the Five Elders and Im below, a slight smile playing on his lips: "We are the Phantom Troupe, we will stand in the heavens."