Ritsu Onodera, a proud literary editor, was tired of being the recipient of jealousy from his co-workers due to his father's clout in the industry. To prove his worth, he quit his job at his father's publishing company and joined Marukawa Publishing. However, instead of landing a job in the literary department, Ritsu was placed as a rookie manga editor in the Emerald editing division. This team operated on tight deadlines, and Ritsu was introduced to the resolute editor-in-chief, Masamune Takano. Interestingly, Takano was Ritsu's first love from high school, and their separation left Ritsu wary of committing himself to another relationship. Now, with the reunion of the former lovers, Takano is determined to rekindle their romance and make Ritsu confess his love once again. Sekaiichi Hatsukoi explores the love lives of three couples within the manga industry, as they all experience their first budding romances.