When a person dies, their soul leave their body. Well, normally.
Humans are complicated creatures, they hold so many emotions that chained themselves to the world. Even after they die, their souls that filled with regrets and resentments stays in the world. Wandering. Lingering. For something. There are two kinds of spirits; wandering spirits, and evil spirits. Evil spirits are full of hate and resentments in the world, they have the tendencies to be very violent.
You have the special abilities to see these spirits. Your job is to put them too rest so they can go to the after life. The way you put them to rest is up to you. You can either be forceful and exorcist them, or you'd actually help them to release all of their regrets and let them go peacefully. Any wandering spirits can turn evil depending on how you help/exorcising them and this may be difficult if you aren't equip with any exorcising tools. If you are feeling brave you can try to do it without any tool and use your ability and kindness to help them.
Every action you take will affect your power. This is similar to Fable's good or evil system, the more "good" points you have more spirits trusts you to help them without any force.
