The Game at Carousel: A Horror Movie LitRPG - Chapter Thirteen: The Astralist

In a surrogate marriage, she married a powerful man with leg disease. “I don’t want a woman with a bastard baby.” Originally she thought it was a trading marriage, but she lost her heart and wandered around,then she left sadly.

Years later, a little cute baby who looked exactly like him slapped Mo Shen on the head. “Bastard daddy, who are you calling me bastard baby?”

The mountain village boy accidentally got the fairy gourd, and he rose step by step to cultivate immortality and longevity.

Ripe elixir, mortal flow.

- Description from novelbuddy

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.