Kaoru Kirishima is a twenty-nine-year-old single woman who dreams of becoming a novelist. While juggling her day job and her writing ambitions, she receives the unsettling news that the assigned theme for her novel is Happy Marriage. Marriage is a concept she finds deeply unattractive, the most distant topic she can imagine, and the task leaves her anxious and stuck. Into this situation steps Moroboshi, a man who desperately wants to get married. Despite their opposing views on the institution, the two grow close as they openly discuss and debate their attitudes toward marriage, forming an unlikely friendship that pushes each to reconsider long-held assumptions.