You can divide the enemies into two basic categories: humans and Yokai, demons that hunt our world. As for the humans, their types can be distinguished by the weapons that they use. However, in case of demons it is more complicated. There are many types of them. From small, theoretically harmless enemies to giant creatures that require a lot of work in order to defeat them.
Each chapter ends with a boss fight. Most of the times, the first try ends with player's death and their knowledge about a boss is that how they look like. The most important thing about those fights is to observe them carefully and learn their moves. Each learned attack and boss' behavior makes the fight easier. The key to success is to move a lot, jump and attack when the moment is right.
There is one more enemy type that you can summon. They are called Revenants. In the locations you can find red markings. They are the places where other players died. When you approach such mark you can see player's name, level, the cause of their death and the difficulty of the fight. You can summon such Revenant and fight with it. When you defeat them you usually get ochoko cups - they allow you to summon other players to help you.