Because Bandai Namco stopped releasing mainline Naruto titles on the legacy PSP hardware years ago, the emulation and modding communities stepped in. They took Ultimate Ninja Impact —the most advanced Naruto game on the PSP—and re-skinned it entirely.
When you download a Storm 6 ISO, you are actually downloading a heavily modified version of one of two official PSP titles: Naruto Shippuden Ultimate Ninja Storm 6 Iso Ppsspp
Modders replace older character slots or expand data files to introduce characters from the late-stage Fourth Great Ninja War and the Boruto: Naruto Next Generations era. You can play as Baryon Mode Naruto, Adult Sasuke, Kawaki, Code, and Isshiki Otsutsuki. You can play as Baryon Mode Naruto, Adult
Adding characters from Boruto or newer Shippuden arcs. Naruto Shippuden Ultimate Ninja Storm 6 Iso Ppsspp
Install the latest version of the PPSSPP emulator from the official site or your app store.