"Yes ka No ka Hanbun ka" centers on the life of Kei Kunieda, a high school student who lives with his overbearing and eccentric family. The Kunieda household is dominated by his father, a former yakuza boss, and his mother, a former assassin, both of whom impose their unconventional values on Kei and his siblings. Kei, however, strives to live a normal life, distancing himself from his family's chaotic and morally ambiguous world. His desire for normalcy is constantly challenged by his parents' bizarre antics and their insistence on involving him in their schemes.

The narrative explores Kei's struggles as he navigates the complexities of his family dynamics while trying to maintain his own identity. His father, Kunieda Sr., often tests Kei's resolve by presenting him with morally ambiguous dilemmas, forcing him to choose between "yes," "no," or "halfway" solutions. These scenarios serve as a recurring motif, highlighting Kei's internal conflict between his family's expectations and his personal principles. Meanwhile, Kei's mother, a sharp and cunning figure, often manipulates situations to push Kei toward embracing his family's legacy, further complicating his efforts to lead a normal life.

Kei's siblings add another layer to the story. His younger brother, Shou, idolizes their father and aspires to follow in his footsteps, while his younger sister, Aki, is more pragmatic but still influenced by the family's unconventional lifestyle. The interactions between the siblings reveal the varying degrees to which each has been shaped by their parents' influence, creating a dynamic and often humorous family dynamic.

Throughout the series, Kei encounters various external challenges, including rival families, former associates of his parents, and schoolmates who become entangled in his family's affairs. These encounters force Kei to confront the reality that his family's past is inescapable, and his attempts to distance himself often lead to unintended consequences. The series balances comedic elements with moments of introspection, as Kei grapples with the moral ambiguities of his family's world and his own place within it.

The central theme revolves around Kei's quest for autonomy and normalcy in the face of overwhelming familial pressure. The series delves into the tension between individual identity and familial expectations, using the Kunieda family's exaggerated antics to explore deeper questions about morality, loyalty, and self-determination. The narrative structure is episodic, with each episode presenting a new challenge or dilemma that tests Kei's resolve and highlights the absurdity of his family's lifestyle. Through these trials, Kei gradually begins to understand the complexities of his family's world and his own capacity to navigate it on his own terms.