As we can read on Wikipedia, a video game based on the popular Devilman manga / anime series was developed by ISCO and published by Namco in 1989 for the NES / Famicom. The game is an action RPG where players take control of Akira Fudo and the objective is to follow clues that will lead the heroes through a ruined city, into underground caves, around a hidden military base and finally into a confrontation with Zenon.
John Doom discovered that in the game’s code are some hidden images, taken directly from the comics, which were not used in the final version. It’s possible that these scenes were meant to be used during the fights against the various demons (Silen, Agwell, Ghelmer, etc.). Another shot shows a dying Miki (as in the comics).
Thanks to John Doom for the contribution and to Jason for the english corrections!