In Part 1, the protagonist Leo Ernst loses his parents in a car accident and is left alone. That’s when Lulu appears, becoming his mother, father, sibling, and friend. In this unfamiliar environment, young Leo begins to develop dreams thanks to Lulu and starts studying to become a chocolate expert. However, as Leo becomes more absorbed in his studies, Lulu gradually fades into the background.

Parts 2 and 3 tell the story of Leo as an adult, now a renowned chocolate artisan. Despite his success, his life is hollow, and he can't even truly taste the sweetness of chocolate anymore. One day, a mysterious child appears in Leo's life. As Leo grows curious and approaches the child, he sees Lulu again. This act of courage and curiosity towards the child breathes life into Leo's dry and desolate routine.