Magical Sapphire is a Kaleidostick-type Mystic Code originally assigned to Luviagelita Edelfelt. She abandoned that contract due to fatigue from constant quarreling between Luvia and Rin Tohsaka, subsequently forming a new partnership with Miyu Edelfelt. As Miyu's magical implement, she enables Miyu's transformation into a magical girl.

Physically, the Kaleidostick features a six-pointed yellow star within a ring, two small blue beads, and two pairs of butterfly-like wings. The upper wings are large and blue with white spots, while the lower wings are smaller and black with jagged edges. A blue retractable handle with a white top and white brush completes the form; the handle retracts when not actively wielded.

In disposition, Magical Sapphire exhibits a more mature, formal, and duty-oriented personality than her older sister, Magical Ruby. She approaches her responsibilities seriously and adheres strictly to directives, contrasting Ruby's mischievous tendencies. This formality occasionally leaves her vulnerable to Ruby's excessive teasing or scheming. While loyal and caring towards masters she deems worthy, she can display formal rudeness towards those she judges unworthy.

Functionally, Magical Sapphire grants access to the Mana Plane, providing near-unlimited magical energy constrained only by the user's Magic Circuits. Capabilities include projecting and manipulating pure magical energy, generating A-rank magical barriers, bestowing physical protection and regeneration, enhancing strength, and enabling flight. She retains autonomy in partner selection and can establish temporary contracts with others if necessary. Her capacities also include hypnosis for memory manipulation, carrying the side effect of reducing the target's IQ. Like Ruby, she cannot access her magical abilities without a wielder, and prolonged separation from a master reverses transformations.

A key operational feature is her ability to perform "Include" and "Install" functions with Class Cards, integrating Heroic Spirit powers into her user. She maintains direct communication capabilities with Ruby via wireless video/audio or physical cable connection, though strong magical interference can disrupt this link.

During the "Prisma Causeway" event, Magical Sapphire was transported alongside Miyu into a Reality Marble created by the First Lady. Separated from Miyu after her capture by Connacht ☆ Medb, Sapphire located Miyu restrained within the Anti-Magical Girl Mystic Code, Voile de Deuil, in the First Lady's castle. Following Miyu's instructions, Sapphire recorded a warning message urging Illya not to approach directly due to the enemy's danger. She delivered this message after temporarily contracting with Mash Kyrielight to fend off an attack by Mini Cu.

In the 2wei Herz! OVA "Magical Girl in Hot Springs Inn," Magical Sapphire accompanied Miyu and others to a hot springs inn. Unique hot springs properties caused increased mana drain for Kuro, necessitating compensatory mana supply activities from Illya and Miyu. Sapphire participated in investigating a magic point that restored the hot springs' properties.

During the confrontation with the Eighth Class Card, Gilgamesh, Magical Sapphire combined with Magical Ruby to form the Kaleido Liner Zwei configuration. This fusion granted Illya the power to defeat Gilgamesh and rescue Miyu, demonstrating Sapphire's capacity for synergistic operation.