The Spirited Daughter-in-law and the Mountain Man - Chapter 903 - : 903 Voluntarily taking it is a slow-acting medicine.

Ronnie, a college student with a boring life has everything around him change when his whole world is turned upside down by a woman he accidentally summons while trying to summon a magical familiar as a game.His peaceful and tranquil days are disrupted as he tries to help her fit into human society while also searching for a way to break their bond.Hell further breaks loose when he discovers that his familiar is indeed the demon queen and mysterious forces start trying to eliminate him for reasons unknown.He struggles to protect himself, adjusting to having a demon queen in his life, and understanding his growing feelings for her.

After transmigrating to the Great Desolation world, he became Dijun.At first, he did not want to be this demon emperor, just wished to be a carefree innate sage. However, appointed by the Dao Ancestor Hongjun, he had no choice but to take on this heavy responsibility.As for the war between the Witches and Demons, Dijun is not interested at all, he only wants to lead the demon clan in building the Great Desolation, and win the favor of heaven and earth, earning virtues and fortune.And the Zhou Tian Star Array, was it created for battle? Dividing day and night, establishing the four seasons, transforming chaos into innate aura, benefiting the Great Desolation, this is the true purpose of the Zhou Tian Star Array.With virtues and fortune upon them, who dares to provoke the demon clan?Under Dijun’s leadership, the entire demon clan continually contributes their strength to the construction of the Great Desolation.

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

Having lived a normal life all his life and died without being able to fulfill his desire and when he’s given a task by a god, watch how he takes the protagonists girls while making it hard for the hero.