Sun Sherard, alias San, emerges as a pivotal protagonist introduced during a high-stakes magical exam alongside her cousin Forte Sherard. A Leap Day birth grants her the rare February 29 birthday, complemented by a B blood type and mastery of summoning magic. Her childhood unraveled tragically when her mother, Saria, succumbed to illness, leaving San ostracized by relatives who branded her a cursed harbinger of misfortune. Barred from Saria’s deathbed, San found solace solely in Forte, their bond forged through shared loneliness. Each July 17, she visits her mother’s grave in the magical realm, a ritual anchoring her to this unresolved grief.

San’s vivacious, mischief-driven persona shines through pranks like coercing Forte into cross-dressing and a speech pattern peppered with trailing musical notes, lending her words a sing-song lilt. She devours meals with gusto, routinely badgering Forte for snacks, and approaches the lethal magical exam with playful irreverence. Though initially scheming to assassinate Nina Yamada for the Crystal Pearl, San unexpectedly bonds with her rival, sharing cake and camaraderie. Her rapport with Zero blossoms into alliance during events like the Kimodameshi, blending competition with collaboration.

Her dynamic with Forte evolves from familial devotion to charged emotional complexity. While the series creator downplayed mutual romance, their interactions simmer with unspoken affection. The manga’s climax sees San storming Forte’s arranged marriage to Rokka, publicly confessing her love—a sentiment he echoes. They vow eternal partnership, though their marital status stays undefined. A sequel set two years later depicts them tackling advanced exams, employing tactics like caging Nina to non-lethally claim the Crystal Drop. Despite recurring failures, their partnership persists, adapting seamlessly to human-world challenges.

Crises unveil San’s resilience: she implores Forte to prioritize survival during Nina’s kidnapping and Zero’s demise, her pleas underscoring a vow against abandonment. This vulnerability contrasts her earlier antics, tracing her growth from trickster to a protector who aids allies against foes like Joker and Al. Her later endeavors balance strategic cunning with unwavering loyalty, cementing her as an eccentric yet steadfast guardian.

No supplementary media beyond core manga and anime adaptations document her story.