Oh no, how did I become the godfather of the demon world?

A fantasy story of cross-temporal linkage between the young Lin Yi and his grandfather Lin Jiu, who has traveled to the Demon Realm. Lin Jiu leads an army in the Demon Realm to resist the rule of the Demon Lord and urgently needs modern weapon support; Lin Yi burns paper model weapons to teleport real ones to the Demon Realm to assist in battle. Lin Yi gains the cultivation level of Golden Core in reality, treats the old master of the Su family, and makes a marriage contract with Su Xiaoxue. He joins forces with the Su family to establish a paper model company, continuously supplying military equipment to his grandfather, and even uses modern weapons such as missiles to defeat the combined forces of immortals and demons. Finally, Lin Jiu becomes the Demon Emperor, and Lin Yi chooses to stay in the human world with his beloved, bringing the story to a close in warmth and victory.

Synopsis from DramaGo.