In Felicidad Underworld, farmers who can produce monsters from seeds and befriend them are called Farmagia. One of the world's five continents, Avrion, is home to a spirited Farmagia, Ten, and his friends—Chica, Arche, Leii, and a fairy named Lookie-Loo. They spend their days in peace, cultivating their fields alongside their monsters.

Everything changes when the Magus, the leader of Felicidad, unexpectedly dies. Oración Seis, the six generals serving the ruler directly, choose one of their own, Glaza, as the new Magus. However, Glaza plans to renounce those without powers and elevate only the talented ones. Worse still, his forces attack Avrion to separate it from the rest of the world.

With the help of their allies, Ten and his friends resist the invasion. The party, each with their own creatures, must now rise up and fight to save Felicidad from imminent doom.