Gwisin Byeolgok

Gwisin Byeolgok (귀신별곡) is a 9 volume Manhwa series written by Han Hyun-Don. It focuses around the exploits of a fifteen year old novice shaman called Ahryung and a ghost by the name of Nachal. According to a deal made by Ahryung's mother, Cheo Yeon, Nachal was supposed to take over her body once she turned fifteen. However, Ahryung has a seemingly endless supply of Yin and proved too strong to be taken over. Instead they make a contract with each other and join forces to combat demonic creatures called Reapers, who are also after the massive amount of Yin in Ahryung's body.

Predator

 * Cheo Yeon

Prey

 * Ahryung

Scenario
The Reaper Yacha takes control of Cheo Yeon, who turns into a humanoid slime creature and nearly tricks Ahryung into letting it absorb her. She breaks free, only for the creature to transform into a giant bird-like monster. After a brief fight, Ahryung attempts to free her mother from Yacha's influence, but the monster takes the opportunity to pounce on her and devour her in one gulp. This in turn transforms Cheo Yeon into an even more powerful monster.

In the following chapter, it is revealed that this was part of Cheo Yeon's plan to break free of her dependence on Yacha. By merging with her daughter, she acquires enough Yin to survive on her own and turns against her master, decapitating him. She then fulfills her daughter's request to revive Nachal, suggesting that Ahryung is still alive inside her.