Some versions are distributed as .ipa files that require tools like AltStore or Sideloadly to install on iOS without a jailbreak. Popular Naruto Mugen Variants for Mobile
Mugen natively runs on Windows (.EXE) and Linux. iOS requires apps to be sandboxed, code-signed by Apple, and distributed via the App Store. Since Mugen uses unlicensed, copyrighted characters and music, Apple will never approve a Naruto Mugen app on the official App Store.