No Gain No Love follows the story of Son Hae-young, a woman who calculates the cost-benefit ratio of every situation in her life. Fearing that she will lose out on a promotion at work due to her single status, she decides to stage a fake wedding. To pull off this elaborate ruse, she recruits Kim Ji-uk, a part-time convenience store worker known for his kindness and integrity, to be her fake groom. As the two navigate the complexities of their contractual relationship, the lines between reality and performance begin to blur. Hae-young, who refuses to suffer any financial or emotional loss, finds her carefully constructed life challenged by Ji-uk's genuine nature. The series explores themes of ambition, the transactional nature of modern relationships, and the unexpected ways love can disrupt even the most calculated plans.