Lazuli-chan is a white-furred hamster introduced in the later episodes of the series, first appearing in the episode that marked the transition into the Hamtaro Paradichu arc. She is visually distinct among the Ham-Hams, with a tuft of white and blonde hair tied up in a ponytail by a red ribbon dotted with white polka dots, and she carries a small bag where she keeps her magical seeds. She lives with her older sister, Lapis, on a large animal reserve called Animal Land, and they are cared for by a kind elderly man who rescued both sisters during an expedition in the desert after they were lost in a sandstorm. The two sisters reside in a house hidden in the forest known as Jewel House, which becomes the central meeting place for the Ham-Hams during this arc. Inside Jewel House is a door that leads to a magical dimension called Sweet Paradise, a world made entirely of sweets, which Lazuli is credited with creating or overseeing through her inventive magic.

Lazuli's personality is notably childish, cheerful, and carefree. She approaches life with a sense of play and curiosity, often acting without considering danger because she finds risky situations exciting. She is bold and openhearted, making friends easily and delighting in sharing her experiments and creations with others. Her youthful and innocent demeanor makes her a natural playmate for younger characters like Penelope, and she is more outgoing and trusting than her protective older sister. Despite her tendency to be reckless, she has a good heart and is always happy to help her friends. She looks up to Lapis for guidance and daily care but also chafes under her sister's overprotectiveness at times.

Lazuli possesses considerable magical abilities, which are described as more powerful than those of her sister. She can brew potions, grow magical seeds, and use a cauldron to scry distant places or teleport the group to other locations. Her most prominent creation is Sweet Paradise, a fantasy confectionery realm fueled by a powerful gemstone that the sisters treasure. She also owns a magical hourglass that imposes a time limit on visits to that world. These abilities make her a valuable ally, especially when the group faces magical threats, and she plays a central role in guiding the Ham-Hams through the adventures of the Paradichu storyline.

Her most important relationship is with her sister Lapis. The two are opposites in temperament: Lapis is cautious, serious, and maternal, while Lazuli is impulsive and lighthearted. Lazuli relies heavily on her sister for protection and daily routines, and she often seeks Lapis's approval, but they also have conflicts when Lazuli's boldness leads to danger or when Lapis becomes too smothering. Lazuli also shows a particular fondness for Snoozer, a sleepy and philosophical hamster. She often mentions him before the others, worries deeply when he is in peril, and appears to enjoy his company, suggesting a close bond that reflects the series' pattern of pairing opposite personalities. Over the course of the arc, Lazuli's involvement with the other Ham-Hams helps her grow more independent while still valuing her sister's care. Her notable character development comes through these moments of reconciliation and shared adventure, as well as the bittersweet conclusion where the gemstone's power is expended to defeat a villain, severing the link to Sweet Paradise and forcing the sisters to adapt to a less magical but still connected life with their friends.