After defeating him, you will automatically get Zero's Buster from him. Defeat him but make sure you do not have the arm upgrade. Keep playing until you fight Vile the second time in Sigma Palace 3. Get all upgrades for Megaman, except for the arm upgrade.
Then, load the cleared saved game to have infinite energy for your weapons. Successfully complete the game with Vile. Successfully complete the game with X to unlock Vile and the Megaman X anime movie. Successfully complete the game to unlock an alternate title screen.
Note: This game is also titled Irregular Hunter X.
