A good leader will use charcoal to mark her colleagues. Sometimes if leaders aren't around all the time, people will get rebellious and act badly toward people who can get them in trouble. So when you mark them with charcoal you know that someone close with your leader is around and you should probably stop being a butt.
You have to be good around her colleagues, because if you aren't your row (りょう) boat permit will be taken away. Row boating is the only fun you ever get to have, besides learning kanji. So act as best you can around the leader's colleagues so you don't lose your row boat rights.