"Otōto no Kuse ni" centers on the relationship between two brothers, Haru and Shō, who navigate the complexities of family dynamics, personal growth, and societal expectations. Haru, the older brother, is a responsible and hardworking individual who has taken on the role of caretaker for his younger brother, Shō, following the death of their parents. Shō, in contrast, is carefree, mischievous, and often relies on Haru for support, creating a dynamic where Haru feels both burdened and protective.

The narrative explores the tension between Haru’s desire for independence and his sense of duty toward Shō. Haru struggles to balance his own aspirations with the responsibilities of raising his brother, often feeling resentment but also deep affection. Shō, while seemingly indifferent to Haru’s sacrifices, gradually reveals a deeper understanding of his brother’s efforts, leading to moments of vulnerability and emotional growth.

As the story progresses, the brothers face various challenges, including financial struggles, interpersonal conflicts, and societal pressures. Haru’s attempts to establish a stable life for both of them are frequently disrupted by Shō’s impulsive behavior, yet these incidents also serve as catalysts for their evolving relationship. The manga delves into themes of familial love, sacrifice, and the complexities of sibling bonds, portraying both the frustrations and the unspoken loyalty that define their connection.

Secondary characters, such as Haru’s coworkers and Shō’s friends, provide additional layers to the narrative, offering perspectives on the brothers’ relationship and influencing their decisions. The story’s pacing alternates between lighthearted moments and poignant reflections, capturing the nuances of their daily lives and the emotional weight of their shared history. Through its exploration of brotherhood, "Otōto no Kuse ni" presents a heartfelt and realistic portrayal of the challenges and rewards of familial responsibility.