Gensei Kaitō Den is set in the same world as Gensei Kitan. Important characters from Gensei Kitan (including its protagonist, the dog Smash) appear in the game, and some of them are playable. However, the main hero is a young and very ambitious thief named Ali-Baba - who is, naturally, the leader of a band of 40 robbers. The game is divided into chapters; each one describes an episode from Ali-Baba's "career", from train robbery to treasure hunt and even discovery of the magic lamp .

The game is a humorous "light" Japanese-style RPG - there is no world map, and most of the time the hero is taken to a new location automatically. Many locations have simple puzzles to solve, and some dungeon areas are maze-like. The gameplay system is nearly identical to that of Gensei Kitan, with the same interface and overall structure. Random enemies are fought in turn-based style, on a side-view battle screen. Characters use physical attacks, special techniques, and magical spells. As in all Gensei games, HP, SP, and MP are fully restored by level up.

Gensei Kaitō Den is set in the same world as Gensei Kitan. Important characters from Gensei Kitan (including its protagonist, the dog Smash) appear in the game, and some of them are playable. However, the main hero is a young and very ambitious thief named Ali-Baba - who is, naturally, the leader of a band of 40 robbers. The game is divided into chapters; each one describes an episode from Ali-Baba's "career", from train robbery to treasure hunt and even discovery of the magic lamp.