17-year-old teenagers - Muscovite Sasha and Kazakh Mamazhan - find out that their parents are going to get married, and now they will become half-brother and sister and will live under the same roof. Soon both realize that peaceful coexistence is impossible: Zhan prevents Sasha from making a sports career, and Sasha Zhan from making music. To get rid of each other, teenagers enter into a confrontation that leads to unexpected consequences for both.