[Crossover] I Used to Be Really Strong

A mysterious System attaches itself at random. When someone says, "[Name], I used to be really strong," the seal will break, and a wondrous adventure will begin. Including, but not limited to: In JoJo's Bizarre Adventure: Bruno Bucciarati and Haku from Spirited Away Yukako and Kars Anasui and Diavolo Josuke and Tetsuya Kusakabe (I feel like this swap won't lead to much) Polnareff and (I forgot...) In Jujutsu Kaisen: Nanami and Yoshikage Kira Gojo and Kakashi Inumaki and Killua (or Gojo and Killua, Bucciarati and Gojo (a voice actor joke)) Ijichi and Sakamoto Junpei and Kichimura Washuu (or Lucifer) (There's also a video with Sukuna and Sanemi, but I won't swap them. I feel like there's not much room to work with.) JoJo's Bizarre Adventure, Bungo Stray Dogs, Jujutsu Kaisen, Hunter x Hunter, and more. It's a big face-swap crossover, inspired by a type of video (all kinds of hilarious ones). Feel free to suggest more similar ideas. Theme: Don't let anything go to waste.