The story of "Sekaiichi Hatsukoi" is about Ritsu Onodera, an editor assigned to the Emerald Editorial Department of the publishing company Marukawa Shoten, who struggles with both work and love as a subordinate to Masamune Takano, the editor-in-chief and her first love from high school. Ritsu changes jobs, vowing never to fall in love again, but panics when she reunites with Takano. She strives to become a full-fledged manga editor, and progresses step by step in both love and work.