"Hōzuki-san Chi no Aneki" centers on the daily life and interactions of Itsuki Aoyama, a high school student, and his older stepsister, Makoto Hōzuki. The story begins when Itsuki’s father remarries, leading to Makoto moving into the Aoyama household. Makoto, a college student, is strikingly beautiful, confident, and often teases Itsuki with her bold and flirtatious behavior. Despite her playful demeanor, she genuinely cares for her younger stepbrother and often supports him in her own unconventional way.

The narrative explores the evolving relationship between Itsuki and Makoto, blending comedy, slice-of-life elements, and light romantic tension. Itsuki, initially flustered by Makoto’s antics, gradually becomes more accustomed to her presence, though her teasing continues to test his patience. The dynamic between the two is further complicated by the presence of other characters, including Itsuki’s classmates and friends, who often misinterpret the nature of his relationship with Makoto.

Makoto’s character is defined by her outgoing personality and her tendency to push boundaries, often creating humorous and awkward situations. Itsuki, on the other hand, is more reserved and struggles to navigate the challenges of adolescence while dealing with Makoto’s provocations. The series balances these interactions with moments of genuine warmth and familial bonding, highlighting the complexities of their blended family.

Throughout the story, the focus remains on the comedic and heartfelt moments shared between Itsuki and Makoto, as well as their interactions with the supporting cast. The manga avoids heavy drama, instead opting for a lighthearted tone that emphasizes the quirks and growth of its characters. The relationship between the step-siblings evolves naturally, with moments of vulnerability and mutual understanding adding depth to their bond. The series concludes with a sense of closure, leaving the characters in a place of growth and connection.