Five years ago, during her early days as a new employee, Seo Gang-jae was a nightmare of a mentor to Jeong Morae. Now, he has returned—as an executive director of SG Electronics with a prestigious lineage, and her direct superior. Haunted by the dark memory of a drunken one-night stand with him at a farewell party, Morae tries to avoid him. But Seo Gang-jae summons her to his office, uses that mistake as leverage, and makes a bold proposal: "Starting now, for exactly three months, once a week—twelve times in total. Sleep with me."