Milo resides in the Principality of Artoria, a 13th-century medieval European-style kingdom. As the son of the court painter serving Artoria Castle, he shares a childhood friendship with Princess Claire. They frequently conducted painting sessions near the stone castle on a lake island, with Claire modeling for Milo. When Claire vanished into the Lost Forest through a spacetime anomaly, Milo stayed in Artoria. Four years elapsed during her absence, causing Milo to age significantly while Claire remained unchanged upon returning with Nobita and Doraemon. A fortune teller attributed her disappearance to a curse by the legendary demon Esael. To console the grieving king and queen, Milo's father painted Claire’s portrait. During Claire’s absence, Milo honed his artistic skills and drafted architectural blueprints. Doraemon later used these plans with the "Water Building Construction Machine" to erect a castle. However, Milo struggled to recreate the irreplaceable Artoria Blue pigment—derived from a rare stone at the lake’s bottom—needed for Claire’s eyes in her portrait. This pigment’s unique shade held greater future value than diamonds due to its irreproducibility. Guiding Nobita on drawing, Milo advised him to "draw what you love while thinking that you love it," prompting Nobita to sketch Doraemon with crayons. During the battle against Esael—freed from a painting by antagonist Sodro—Milo drew a functional slingshot using "real crayons." Nobita fired the "water-processing sprinkle" from this slingshot into a building constructed from Milo’s blueprints, dissolving Esael into water and restoring color to Artoria. Post-battle, the rediscovery of the Artoria Blue stone allowed Milo to complete Claire’s portrait. The painting that initially transported Claire to the present was revealed as altered: it showed her in the forest alongside Chai, a transformed red bat, and included added depictions of Milo, Doraemon, and others. A child’s crayon drawing resembling Nobita’s sketch of Doraemon was also uncovered, though critics dismissed its worth.