Devilman

The game follows the manga's story.

You start as Akira Fudo the boy who has the ability to change into Devilman. You wander around the town going into houses and talking to the people you find. When you find your friend Ryo he transports you to a basement room where you change into Devilman and battle on-coming hordes of girls who transform into demons. If you manage to survive you return to the town. Now in between talking to the inhabitants you can increase your energy bar by defeating the monsters that roam around outside. You can change into Devilman and back by pressing select and choosing to change up or down.

Defeating monsters as Akira gives you more power when you are Devilman. This power allows you to fire fireballs when you press punch but the more you do this the more your power (represented by Devilman heads) decreases. If you visit Akira's friend Miki Makamura (in the guise of Akira) she will give you your energy back. In fact at one point in the game you play as Miki. Then later still you can use Devilman's wings and fly to the mountains or the woods. Here you must find and save (or not if you choose) the humans trapped by demons.