Play Just Run become the leader the people are looking for.
Just Run 3D is all about bringing people together. To assimilate a new member into your little army all you need to do is approach a random same color. They will automatically join you becoming the same color as you. The more people you run into, the bigger your crowd becomes, but you should always be aware of other obstacles:
You start out as a single person running other people to join you. Evidently, your character is pretty charismatic: when you run into a neutral NPC you quickly convince them to become a member of your party. The goal is to create the biggest crowd and go to the castle to defeat the enemy.