七月（马思纯饰）是个乖巧懂事的13岁少女，她成绩优异，是老师眼里的好学生，家长心中的乖孩子。有一天她们班里转来一个名叫安生（周冬雨饰）的女孩。安生性格冷漠，放浪、不羁，经常不按常理出牌，她和班里的同学总保持着距离。这两个性格迥异的女孩却相互吸引着对方，慢慢地成为一对最要好的朋友，原本她们以为这辈子都会陪着对方。但是随着她们的成长，她们的友谊也发生了变化。在她们18岁那年，二人遇到阳光帅气的苏家明（李程彬饰），这一对闺蜜同时爱上这个优秀的大男孩。而苏家明对稳重乖巧的七月和个性张扬的安生生出好感。一方面他觉得长相漂亮性格温顺的七月更加适合他，可是他又忍不住被叛逆的安生所吸引。就这样一个男人和两个女孩之间开始了一段剪不断理还乱的三角恋情

Qiyue (played by Ma Sichun) is a well-behaved and sensible 13-year-old girl. She has excellent grades. She is a good student in the eyes of teachers and a good child in the eyes of parents. . One day a girl named An Sheng (played by Zhou Dongyu) was transferred to their class. An Sheng is indifferent, unrestrained, and uninhibited, and often plays cards out of common sense. She always keeps a distance from her classmates. These two girls with very different personalities are attracted to each other and gradually become a pair of best friends. They thought they would stay with each other for the rest of their lives. But as they grew up, so did their friendship. When they were 18 years old, the two met the sunny and handsome Su Jiaming (played by Li Chengbin), and the pair of girlfriends fell in love with this outstanding boy at the same time. And Su Jiaming has a good impression of the steady and well-behaved Qiyue and the flamboyant An Sheng. On the one hand, he thinks that the beautiful-looking and docile Qiyue is more suitable for him, but he can't help but be attracted by the rebellious An Sheng. In this way, a love triangle began between a man and two girls