Airi, a bright and innocent girl entering adolescence, is in the midst of physical development as her body gradually matures. Though she struggles with academics, she's deeply curious and enthusiastic about sex. Through conversations with friends and reading manga, she learns about masturbation and begins exploring her desires. Driven by hidden longing and curiosity, she grows increasingly drawn to her older brother. As her body blossoms, so too does her emotional world—this is a story of one girl's coming-of-age, filled with pure affection and yearning.