Two-dimensional girls referred to fictional characters that existed in anime, manga, games, and other two-dimensional cultures. They usually had exaggerated appearance characteristics and personalities, while three-dimensional girls referred to human women who existed in real life. The difference between 2D girls and 3D girls was the virtual and real space they existed in. Two-dimensional girls only existed in virtual worlds such as anime, manga, and games, while three-dimensional girls were real human women living in the real world. In some novels, there might be a situation of mutual transformation or confusion between two-dimensional girls and three-dimensional girls, such as two-dimensional girls crossing into the real world or becoming a part of three-dimensional girls. These plots were usually regarded as fictional plots with no practical significance.