Sites like CrazyGames and Unblocked Games 66 have dedicated "Mugen Unblocked" sections. If your school blocks them, add https:// and use a free proxy extension (like UltraSurf or Hola ). Only use VPNs if your school’s IT policy allows it.
Here is a conceptual look at how the "Instant Play" button would function: Mugen Unblocked
How to assemble a simple, safe portable M.U.G.E.N package (high level) Sites like CrazyGames and Unblocked Games 66 have