An adaptation of "Dear Brother" (1974) by Riyoko Ikeda, an insecure and lonely girl named Nanako Misonoo starts as a freshman at Seiran Academy, a prestigious girls' school known for its sorority members who do not always meet the usual criteria. Despite this, she is unexpectedly chosen to join the sorority, which attracts envy and bullying from those left out. Meanwhile, she becomes close to Mariko Shinobu, a troubled student with whom she shares feelings but struggles to share Nanako's company. Struggling with conflicts, rivalries, and everyday life issues, Nanako confides in her surrogate brother Takehiko Henmi through letters. Takehiko is a college student who was Nanako’s favorite tutor during that time, remaining close to her despite not knowing she knew about his dual identity as her paternal half-brother, the result of her father's previous marriage.
Dear Brother
Nanako reunites with her childhood friend Tomoko at an exclusive all-girl high school, where they encounter affluent students. The drama revolves around their experiences and adventures during Nanako's teenage years, as she keeps a diary of these events for her estranged brother.