I think the sidekicks are for making the story richer. Sidekicks, they can be antagonists like anonymous villains in Konan and good assistant like Watson of Sherlock Holmes. Imagine a story with only one or two main characters, will it be fun? Certainly, it won’t be. The story cannot be interesting and attractive if there is no one helping and leading the story to be continued. Not only making story fun, they also create tensions, tragedies and comedies by causing troubles and complications or making some jokes. By that way, the story goes through the rising action and also the climax, and then eventually the ‘adventure’ of the major character starts with help of those sidekicks. Like these examples, the sidekicks are also the essential elements of stories.