Guide to Failing as a Full-Level Green Tea - Chapter 257.1 - Don’t Worry

Before his gruesome death, Gene Conti was one of the greatest icons of the 1960s. But after spending half a century in Hell, only gambling and the suffering of others excite him.Fortunately for him, his days of boredom are over. Having served his sentence, he finds himself in the body of a young man in the modern era.Now freed, Gene wishes to continue what he missed the most as a dead man: acting.Once again, he aspires to be an actor admired the world over.But will the angels and demons leave him alone? Will his bold attitude clash with the sensitive modern era? Or will the actor from Hell surrender to his lust for chaos and violence?

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

It was supposed to be a perfect deal in which both parties got what they needed. However, after the child was born, he tore up the agreement with discontent and told her, “Who said that we’d only have one child? I want twins! Twin brother and sister! You’ll continue giving birth to more children until you bore me a pair of twins!”

I became the childhood friend of the protagonist in a novel. The childhood friend who died from taking drugs.