Extra's Perfect Ending - Chapter 302: Climbing

As he transmigrates across the continent of Douqi, Gu He takes on the mantle of Alchemy King Gu He and gains an incredible power - the Ten Thousandfold disciple cashback system. This allows him to grant gifts to his disciples, which are then returned ten thousandfold.“You have gifted Liu Ling the Green Lotus Core Flame, triggering a tenfold return and granting you the mighty Green Lotus Holy Fire!” the system announces as each gift brings Gu He greater power.After three years of intense training, Xiao Yan returns proudly to the Yunlan Sect, eager to display his newfound strength.“Don't underestimate this once poor youth!” he warns his former lover Nalan Yanran. “Today I'll show you what a true genius can do!”But Nalan Yanran just smiles faintly. “Is that so?” she asks, as a terrifying Dou Emperor aura suddenly surges from her.Shocked, Xiao Yan stammers in disbelief, “How did you become a Dou Emperor powerhouse?”With an arrogant smile, Nalan Yanran replies, “With my master, anything is possible.”

Liu Duo was a young girl whose grandmother sold her to four brothers with the intent to be a bride. Unwilling, she ran away the following night, only to fall unconscious while trying to get away. Unexpectedly, however, she was reborn with the spirit of a 25 year old woman, also named Liu Duo.

- Description from Novelupdates

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.