Leonardo da Vinci is a Servant affiliated with the Chaldea Security Organization. Historically recognized as a universal genius from 15th to 16th century Europe, this figure left a profound influence on the advancement of civilization. Although recorded as a handsome young man in life, the Servant manifestation embodies the Mona Lisa—the ideal beauty pursued during their lifetime—a change attributed to a personal desire to become a beautiful girl, reflecting a belief that cultural norms might one day accept such a form as standard. This Servant exhibits a rational and placid personality, maintaining composure through an ability to accurately assess any situation. A strong interest in fascinating subjects can provoke lively enthusiasm. Fully aware of their own omnipotence, they understand precisely their limits and the capabilities of others. Eccentricities include a habit of eavesdropping, a particular fondness for birds and wing-themed designs, and a tendency to roam nude after bathing regardless of others present. The character openly admits to being a pervert. As the third Heroic Spirit summoned by Chaldea while its summoning system was still incomplete, this Servant chose to remain due to interest in its circumstances and through persuasion by Romani Archaman. A duplicate puppet was constructed to serve as a Master, allowing the Servant to remain suspended in the present era—a technique similar to that of a certain doll maker. Within Chaldea, they serve as Special Honorary Advisor of the tech division, providing mission planning support and technical backup during operations like ray-shifts. They form a contract with Ritsuka Fujimaru, the Last Master of humanity, acting more as a teacher close in age than a great mentor. This relationship takes on a comedic tone, with simple questions from Fujimaru swaying various heroic spirits. Relationships with other figures are noted: Romani Archaman is a close friend and colleague; Makiri Zolgen is recognized as an acquaintance and excellent magus from early years; Michelangelo is considered one of the few true friends and an equal in fine arts, despite historical rivalry; Sherlock Holmes is viewed as an irritating genius who requires monitoring. Specific, though partially obscured, thoughts are held regarding another individual referred to as "■■■■ ■■■■■". A later version, known as the young girl model or "Gran Cavallo," is a homunculus-like Servant created as a backup by the original. Activated following the original's departure, she has a limited lifespan. While fundamentally identical in personality, she exhibits a more pronounced air of an ingénue, with gentler and more girlish speech patterns. She describes herself as everyone's "Da Vinci-chan, little girl version." Operating without a Master and functioning almost like a human, she expresses anxiety about living up to the original's achievements and longs for experiences inherited only as memories. Her versatility is reduced, akin to a child who cannot reach a high shelf, though her breadth of knowledge remains vast. This younger version maintains a bright, cheerful, and brilliant demeanor toward the Master, acting as an advisor and sometimes as an elder or younger sister. Key relationships include a definitive intention to confront Rasputin, a shared connection with Mash Kyrielight regarding the experience of starting one's humanity anew, and a sense of worry about the eventual end of Sherlock Holmes. Capabilities are multifaceted. As a Caster, skills include high-tier Territory Creation and Item Construction, alongside personal skills like Natural Born Genius EX and Golden Rule (Body) B, which later upgrade to provide defensive, supportive, and NP-related effects. A Noble Phantasm is also wielded. The Rider variant, Da Vinci-chan, utilizes skills such as Golden Rule (Body) EX for debuff immunity, HP regeneration, and NP gauge charging; Accel Turn B for evasion and critical strength; and Dream upon the Star D for party-wide NP strength, gauge, and overcharge support. Her Noble Phantasm, Beautiful Journey, is an Anti-World attack that also charges the party's NP gauges.