Jonas Anders is a young man with blond hair and blue eyes, often dressed in a blue vest over a white shirt with black pants and brown boots. He is the son of a wealthy family that runs a sugar confectionery shop, and he aspires to become a skilled silver sugar artisan like the protagonist, Anne Halford. Initially, he is presented as a confident and charming individual with a prince-like appearance, but this facade conceals a deep-seated arrogance and a self-serving nature. He holds a prejudiced view toward fairies, treating them as possessions rather than sentient beings, which reflects the dark, dominant human attitude of the world he inhabits.

Jonas is a former friend of Anne, having known her when she lived with her late mother. He persistently declares his romantic feelings for her and proposes marriage, but Anne rejects him, believing his feelings stem from pity rather than genuine love. This rejection, combined with his jealousy of Anne's natural talent, drives his actions. He does not truly seek Anne's affection; rather, he covets her exceptional skills as a confectioner to advance his own career. His primary motivation is to win the Royal Candy Fair and achieve the status of a silver sugar master, a goal he believes is rightfully his.

In the story, Jonas serves as a rival and an early antagonist. He catches up to Anne and her fairy bodyguard, Challe, on their journey to the capital, joining their party under the guise of protection. However, his true intentions are vile. He steals a sugar confectionery piece that Anne created, intending to enter it into the competition as his own work. To cover his crime, he sabotages Anne by smearing blood on her clothes to attract wolves, leaving her to die in the forest. His scheme unravels at the competition when a judge notices the similarities between his entry and Anne's new, original piece. Forced to recreate the stolen artwork in front of the judges, Jonas fails spectacularly, revealing his lack of skill and proving his fraud. Anne publicly humiliates him with a slap, and he is disgraced.

His key relationships are marked by manipulation and selfishness. Beyond Anne, he uses an enslaved fairy named Cathy to aid his schemes and attempts to frame another fairy, Mithril Lid Pod, for his thefts. He also has a connection to the Radcliffe workshop, where he is an apprentice, but his reputation there crumbles after his exposure. Later in the series, Jonas suffers under the abusive demands of Duke Alburn, which leads him to further desperate acts, such as taking Mithril hostage to force Anne's compliance. Despite these repeated betrayals, a complex development occurs. After hitting a low point, he draws a line at extreme cruelty, warning Challe when another character, Sammy, plots to boil Anne's hands, thus crippling her career. Eventually, Anne offers him a position at the Paige workshop, starting him on a rocky and not entirely convincing path toward redemption, though he struggles with guilt and avoids confronting his past misdeeds.

As a sugar artisan, Jonas lacks the genuine creativity and technical skill of Anne. He is unable to replicate the intricate designs of her late mother, Emma Halford, and fails completely when forced to reproduce stolen work. His notable abilities lie not in craftsmanship but in manipulation and deceit, using charm and underhanded tactics to try to get ahead. His character serves as a foil to Anne, highlighting her integrity and talent in contrast to his cowardice and entitlement.