Lara Jean Song keeps her love letters in a hatbox her mother gave her. They are not love letters that anyone else wrote for her; these are ones she has written. One for every boy she has ever loved, five in all. When she writes, she pours out her heart and soul and says all the things she would never say in real life, because her letters are for her eyes only. Until the day her secret letters are mailed, and suddenly, her love life goes from imaginary to out of control.