Mom's good friend: Seong-su, who is heartbroken after losing his lover to his best friend Dong-ho, is comforted with all his heart and soul by Yeo-jin, an older woman he meets by chance. Falling in love with her mature consideration, Seong-soo starts dating Yeo-jin, saying it doesn't matter whether she's older or married. But what is this? It turns out that Yeo-jin was the stepmother of her old best friend Dong-ho! The ex-girlfriend she loved passionately. her best friend. She is the mother of a friend who has come to love her the most in the world.