Reina Aharen is the narrative's female protagonist. Her background involves a childhood move following an encounter with a boy at a playground, an event she does not remember. She resides with parents often absent due to work, necessitating her care for younger siblings Ren and Eru Aharen.

Physically, Reina possesses a notably short stature for her age, long silver hair, and deep blue eyes. She typically maintains a stoic facial expression regardless of the situation, even while laughing or crying. Her standard outfit is a school uniform: a dark blue button-up over a white dress shirt, dark navy skirt, long black tights, and brown penny loafers. Her resemblance to her brother Ren is strong enough to cause mistaken identity when he wears her clothes. A defining trait is her perpetually youthful appearance throughout life, eventually leading her to look younger than her own daughter and granddaughter.

Reina's personality centers on complex social difficulties. She struggles profoundly with gauging interpersonal distance, fluctuating between extreme shyness around strangers—speaking nearly inaudibly—and excessive physical closeness or overfamiliarity once connections form. This pattern stems from past ostracization due to social missteps, creating lingering self-consciousness about burdening others. Despite these challenges, she demonstrates deep appreciation towards those who accept her, often repaying kindness through actions like preparing meals or offering assistance. She intensely values friendships, expressing a desire for lifelong bonds with high school companions. Additional traits include a large appetite with rapid metabolism, frequent daytime sleepiness, and significant clumsiness in sports despite gaming proficiency.

Relationships form a core aspect of her development. Her connection with Shōta Raidō begins when he retrieves her eraser, sparking her interest. Their friendship evolves through shared activities and communication efforts, culminating in mutual romantic feelings. A failed confession attempt occurs during a camping trip where she kisses him prematurely, fearing rejection. Their relationship solidifies later when she formally confesses after resolving misunderstandings, eventually leading to marriage. As partners, they maintain similar interaction patterns but gradually show increased affection and emotional openness. With childhood friend Mitsuki Ōshiro, Reina experiences early protective behavior from Mitsuki but later reconciles their friendship after encouraging Mitsuki's acceptance of Raidō. Her sibling relationships involve caring for Ren and Eru, though Eru initially displays hostility toward Raidō due to jealousy.

Reina's development occurs across social and emotional dimensions. Initially isolated due to social anxiety and past experiences, she gradually builds confidence through sustained friendships. Her romantic progression with Raidō transitions from uncertainty to a secure partnership where both discuss insecurities openly. Academically and artistically inclined, she pursues art school education in another prefecture during her third year of high school, later establishing a career as an illustrator. Post-graduation milestones include marriage to Raidō, motherhood, and eventual grandmotherhood while maintaining her youthful appearance.

Notable skills and traits include exceptional craftsmanship and artistic talent, often showcased through manual projects. She demonstrates culinary expertise, preparing elaborate meals from limited ingredients. Gaming proficiency spans arcade, board, and video games, contrasting with poor athletic ability. A running gag involves her immediate mastery of new activities, frequently outperforming Raidō in competitions. Trivia encompasses sharing Raidō's birthday, fearing spiders alongside her siblings, and owning a pet dog named Nui. Her name's etymology incorporates meanings related to "tinkling/exquisite" (玲) and "endure" (奈), while her Okinawan-origin surname connects to narrative setting elements.