Jonas Under, alias Jonas Anders, is the son of a prosperous sugar confectioner and nephew of Marcus Radcliffe, headmaster of the Radcliffe Workshop. He pursues silver sugar mastery with princely confidence, flaunting blond hair, blue eyes, and refined attire: a blue vest, white shirt, black pants, and thigh-high boots. His outwardly friendly demeanor includes persistent marriage proposals to Anne Halford, which conceal deep-seated arrogance and entitlement—particularly toward fairies, whom he treats as possessions.

Jonas plots to exploit Anne’s inherited talent after failing to replicate designs by her late mother, Emma Halford. He manipulates his enslaved fairy Cathy, using her invisibility to sabotage Anne’s work, frame fairy Mithril Lid Pod, and steal Anne’s sugar artwork for the Royal Candy Fair. Jonas abandons Anne in a wolf-infested forest to ensure her death and his sole credit. Anne survives and debuts a new piece at the exhibition. Judges note similarities between entries, forcing a public recreation test where Jonas’s inability to replicate basic elements exposes his fraud. His humiliation culminates in Anne striking him.

Subsequently ridiculed at Radcliffe—especially by apprentice Sammy Jones—Jonas flees when Sammy assaults Anne. He spirals into drunkenness, abandoning sugar crafting entirely. Though cleared of past misconduct, he initially refuses to return to Radcliffe, fearing comparisons to talented peer Keith Powell. Anne eventually persuades him to resume his craft at the Paige Workshop. There, he dedicates himself to skill-building but remains tormented by guilt, avoiding eye contact during a later encounter with Anne and fairy Challe to evade confronting his past cruelty.