The negative effects of time-travel novels or anime on teenagers may vary from person to person, but the following are some possible examples: 1. Misunderstanding and disrespect for historical knowledge. Time travel novels and anime often involve historical events and characters, but sometimes the author or production company may misunderstand and deal with historical knowledge, which may lead to teenagers having a wrong understanding or disrespect for historical events and characters. Escape from reality. Some time-travel novels or anime may allow teenagers to escape from reality by entering a fictional world to obtain temporary comfort and escape stress. 3. The learning of social skills is insufficient. In a novel or anime world, teenagers may encounter characters with different backgrounds and personalities, which may help them learn how to communicate and cooperate with others. But in the real world, these social skills may need to be learned and practiced by teenagers in real life. 4. Fantasy and misunderstanding of sex. In some time-travel novels or anime, gender may become an important theme or character, which may attract teenagers 'fantasies and misunderstandings about sex. But in the real world, teenagers should learn how to view sex and sexual relationships correctly. Time travel novels or anime may have some negative effects on teenagers, but these effects may also vary from person to person. It is important for parents and education workers to supervise and guide teenagers to read and watch time-travel novels or anime to ensure that they understand the background and content of these works and learn the correct values and moral values from them.