Sumire Shinohara serves as the protagonist’s loyal classmate and closest confidante, her romantic heart intertwined with steadfast dedication. Secretly pining for Dai Takabayashi, whose focus lingers on the protagonist, she channels unspoken feelings into unwavering support for her friend and active defense of the Doll Kingdom. As the princess’s trusted aide, she wields a green bracelet acquired later in the series—a counterpart to the protagonist’s pink one—to summon the guardian knight Doll Izumi during critical battles, shifting her role from passive observer to determined combatant. Though naturally timid, she repeatedly summons courage to protect others in peril.

Her stable family life and academic diligence anchor her school persona, complemented by a fondness for crafting imaginative stories and daydreaming about romantic scenarios involving Dai. A subplot sees her bracelet stolen by an antagonist, prompting a rescue mission that showcases her growing resolve. While entangled in a subtle, unresolved love triangle, her gentle demeanor gradually harmonizes with her responsibilities as a protector. Despite evolving challenges, her core traits of kindness and loyalty remain unshaken, persisting through her journey as both a supportive friend and a guardian of the Doll Kingdom.