"365 Days to the Wedding" centers on Takuya Yamada, a 30-year-old systems engineer who leads a solitary life, prioritizing work over personal relationships. His routine is disrupted when his company introduces a new policy requiring employees to be married to qualify for a transfer to the coveted Hokkaido branch. With only 365 days to secure a marriage, Takuya must navigate the unfamiliar terrain of dating and relationships, a challenge he is ill-prepared for due to his introverted nature and lack of romantic experience.

The narrative explores Takuya's attempts to find a suitable partner, often leading to humorous and awkward situations. His efforts are complicated by his limited social skills and the pressure of the ticking clock. Along the way, he encounters Rika Sonezaki, a colleague who initially appears indifferent but gradually becomes a key figure in his journey. Rika, who harbors her own reasons for avoiding marriage, reluctantly agrees to help Takuya in his quest, forming an unlikely partnership.

As the story progresses, the dynamic between Takuya and Rika evolves, blending moments of comedy with deeper emotional undertones. The series delves into themes of societal expectations, personal growth, and the complexities of modern relationships. Supporting characters, including coworkers and potential romantic interests, add layers to the plot, highlighting the diverse perspectives on marriage and commitment.

The manga balances lighthearted humor with poignant reflections on the pressures faced by individuals in a society that often prioritizes traditional milestones. Takuya's journey is marked by self-discovery, as he learns to confront his fears and insecurities while striving to meet the deadline. The interplay between Takuya and Rika serves as the emotional core of the story, offering a nuanced portrayal of two individuals navigating their shared predicament.