My Succubus Sister

[Brother with a Sister Complex + Sister with a Brother Complex. The brother is a rationalist and a psychopath; the sister is an innocent, healing succubus. The characters and setting also take inspiration from Sister Priestess and the Root of Evil.]

Near the end of the war between humans and demons, a legendary hunter found a lost child and raised him.

Ten years later, Lei Xi’s father dies, and his sister’s demonic bloodline begins to awaken. After reading the letter their father left behind, Lei Xi decides to take his sister on a journey to resolve the problem with her bloodline.

Just then, humans begin to mutate, demons return, and the storm gathers.