Uchū Tantei Divan is a follow-up to Jantei Monogatari, though it can be hardly considered a true sequel because of its entirely new setting and themes. Set in a sci-fi environment, the game casts the player in the role of Divan, a young man who possesses the ability to transform into a powerful supernatural being, and is entrusted by military authorities to protect Earth against an alien demonic attack. This can be done only by defeating the evil minions in mahjong games.
Though featuring elements of a Japanese-style adventure game (verb commands that must be selected from a menu to trigger the next scene), the game focuses on mahjong matches against opponents, which occur as dictated by the plot. The game uses standard mahjong rules, with the exception of bonus powers that can be acquired for points distributed after each round and used in subsequent matches.