Imagine, if you will:
Saruto: Otsutsuki Wars. Final Arc. Lord Otsutsuki Otsutsuki of the Otsutsuki clan is in a Jutsu Clash with the 18-year-old Juubi-Saruto, overwhelming them and forcing them to use both Rinnegan and the Rinne-Sharingan. Eidawaki jumps in and uses Shinjutsu to assist them, while Konohamaru Jr. uses his Natural Energy Spirit Bomb to help, but they're all getting beaten.
"No..." Saruto says, "This can't be happening! For everyone back home! For Mom! For Dad! For all of our families! For Mitsuki-Sensei! For the Bijuu and Jinchuuriki that gave their lives to give me this power! For humanity, and the Earth itself, I cannot lose!!!"
A voice emanates telepathically from behind them, and a spectral hand reaches out, grabbing Juubi-Saruto's head from behind.
"So that's where you are... Kurama..."
The Juubi starts moving around, and they sprout additional arms, each with its own Rinnegan and Karma mark. Saruto has no idea what's going on, and a massive portal opens.
Lord Otsutsuki falls out of the portal, and sees Naruto and Hagoromo with the same goatee, and Sasuke and Hamura with the same haircut(Sasuke looks like old Madara), all cracking their knuckles, with billions of people standing behind them, all wearing brass knuckles.
"Now...," Naruto says, "Get ready to feel the power of the ninja world we created! Dattebyo."
10 chapters of every named character punching the villain in the face.