Spring has finally arrived in Moomin Valley, giving way to another great adventure for Moomintroll and the rest of its inhabitants. With Snufkin coming home from his winter migration, the locals of the valley finally begin to rise from their hibernation. Finding a mysterious hat, the Moomins cannot bring themselves to throw it away due to its fine quality, instead hoping to eventually find its owner. While playing games with his friends, Moomin tries to hide in the silk hat. When his friends come looking for him, they are shocked to discover that Moomin has transformed into a hideous creature. Examining himself in the mirror, he is disgusted to find himself completely unrecognizable. Transforming back to normal after scaring his friends and family, Moomin and Snufkin decide to toss the hat in the river. As it drifts away, they begin to wonder who the hat belonged to and whether its owner will return for their lost possession.

When a genius patissier dies in a tragic accident before achieving his dream of creating the world's greatest sweets, he is reincarnated as nine-year-old Pastry Mille "Pas" Morteln. Now in a medieval world brimming with swords and magic, Pas enjoys a peaceful life in the Fief of Morteln under the authority of his father, the military hero Lord Casserole. However, scarce ingredients render sweets a luxury, so Pas can only dream of baking. Once news arrives of approaching bandits, Pas must learn magic and fight to defend his land, all to one day create a confectionery paradise!

Renowned manga artist Hiromu Arakawa has an unusual backstory: she used to work on a farm in Hokkaido, the food warehouse of Japan, for seven years! To her editor, Ishii, harvesting produce and milking cows are foreign concepts; but as the daughter of two multigenerational farmers, Arakawa is there to explain the challenging yet noble job of being a farmer.