Torneco (aka Taloon) from Dragon Quest IV was a merchant and treasure hunter who always dreamed of owning his own shop. Having defeating the evil along with other heroes, he returned to Endor to work peacefully. Some time has passed and after growing successful in this town, Torneco grew anxious. Hearing rumors one day about a "Mysterious Dungeon", Torneco meets with the king to ask permission to set up a new shop, closer to this Mysterious Dungeon. By exploring this cavern and returning safely with the prizes, Torneco hopes to become the most successful merchant in the world.

Torneco no Daibōken: Fushigi no Dungeon is a overhead view game similar to Hack, what might be called a "dungeon crawl". Torneco must venture into the mysterious dungeon gathering treasure. He may equip any weapons and shields he finds there, as well as gather up items such as spell scrolls, staffs and herbs with a variety of effect. A variety of enemies, familiar to the Dragon Quest series, await him. If Torneco successfully exits the dungeon, he is able to sell any of the items he has collected. This money then goes to improve the quality of his shop and living quarters. As the game progresses, Torneco is able to store special items in the vault, which he is then able to bring with him on subsequent trips to the dungeon.