In th early 21st century, Tokyo became the center of advance scientific research. Ground-breaking discoveries were made in the field of computer science, as well as re-discovering the ancient art of magic. A crime organization known as Digital Beast emerged, controlling much of the new technological resources. The organization became so powerful that the authorities were unable to stop its activities. A mercenary named Lightning (or "Light" for short) recently joined a special group named Black Bird. One of his assignments involves investigating strange occurrences in the New Planning company building, which might lead him on the trail of Digital Beast.

Black Bird is a solo dungeon crawler (with auto-map feature): the gameplay consists of exploring maze-like passages in pseudo-3D environment, fighting randomly appearing enemies. The game features card-based combat. Lightning and his opponent are dealt a deck of cards. The goal is to get rid of single cards and to build combinations (three of a kind, straight, etc.), a bit similarly to a poker game. A successfully built combination inflicts damage on the enemy. There are also defense-strengthening and healing cards, which the player can use between the combinations. Beside that, the game has a traditional RPG system with hit points, experience points, leveling up, money management, equipment, etc.

The adult content appears mostly during battles, with enemies who look like pretty girls and remove some (or all) of their clothes when defeated.

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