My Spring Days tells the poignant story of Lee Bom-yi, a woman who receives a heart transplant that saves her life after a terminal illness. Grateful for her second chance, she lives her life with infectious optimism and passion. Her path crosses with Kang Dong-ha, a widower and CEO of a livestock company who is still grieving the loss of his wife, whose heart happens to be the one that now beats inside Bom-yi. As the two grow closer, they find themselves entangled in a complex web of fate and destiny. The drama explores themes of cellular memory, the ethics of organ donation, and the healing power of love. As Dong-ha begins to see his late wife's personality and habits reflected in Bom-yi, he must navigate his conflicting emotions while Bom-yi struggles to understand the mysterious connection she feels toward him and his family.