The advantages of using four main characters in a movie were as follows: 1. Increase the cohesiveness of the story: Usually, there will be multiple protagonists in a film or television series, but it is difficult for the audience to really remember each character. Using four main characters could increase the cohesiveness of the story and make it easier for the audience to get involved in the plot. 2. Prominent the protagonist's personality: The four protagonists can highlight the protagonist's personality and make the protagonist more vivid and interesting. Through the combination of the four main characters, the audience could better understand the character, background, goals, etc. of each main character and thus understand the story more deeply. 3. Increase character interaction: The four protagonists can increase the interaction between the characters and enhance the emotional connection between the characters. For example, the four protagonists could form a team to face a challenge together, support each other, and cooperate with each other to increase their emotional tension and attractiveness. 4. Increase the narrative efficiency of the story: Using four protagonists can tell the story faster because each protagonist can be independent and not like multiple protagonists who need to narrate in parallel. This could also increase the production efficiency of the film and shorten the filming cycle. In short, using four main characters could better attract the audience's attention, enhance the attraction of the story, and increase the production efficiency of the film.