Nokkers

Knockers (ノッカー) are unknown creatures that were created to impede Fushi's progress in preserving the world.

Abilities
(more to be added)
 * The Knockers have the ability to steal Fushi's forms from him, along with his memories of that form. For example. when the Knockers steal March's form from Fushi, he is completely unable to remember her. He isn't even aware that anything was stolen from him.
 * They also have the ability to adapt to their environment. Fushi first encounters the Knockers in the forest and at that time, the Knocker was made up of vines and leaves. The next time Fushi encounters a Knocker, it is made up of rock.
 * The Knockers seem to be able to control living people. In chapter 48, the Knockers take control of Uba's body. She seem to be aware of what she is doing but is unable to control her movements. It is later revealed that a person dies almost immediately after the Knocker takes control of their body.