"Kyo→Dai Dakara Nandayo!?" centers on the lives of two siblings, Kyosuke and Akane, who navigate the complexities of their relationship while dealing with the challenges of adolescence. Kyosuke, the older brother, is a high school student known for his laid-back and carefree demeanor, often finding himself in humorous or awkward situations. Akane, his younger sister, is more serious and responsible, often acting as the voice of reason between the two. Despite their contrasting personalities, they share a close bond, though their interactions are frequently marked by playful bickering and sibling rivalry.

The narrative unfolds through a series of episodic chapters, each highlighting the siblings' daily lives and the humorous or heartfelt moments that arise from their interactions. The story explores themes of family, growing up, and the unique dynamics of sibling relationships. Kyosuke’s tendency to get into trouble or misunderstand situations often leads to comedic scenarios, while Akane’s attempts to keep him in check provide a balance of humor and warmth.

Supporting characters, such as their classmates and friends, add depth to the story, contributing to the comedic and emotional moments. The manga balances lighthearted humor with occasional moments of introspection, offering a relatable portrayal of the ups and downs of sibling life. The episodic structure allows for a variety of situations, from school events and family gatherings to more personal challenges, ensuring a dynamic and engaging narrative.

Overall, "Kyo→Dai Dakara Nandayo!?" presents a charming and humorous exploration of sibling relationships, capturing the essence of familial bonds through its well-developed characters and relatable scenarios.