MTL - From the Head Pillar Tanjiro, Take Stock of the Wonderful Nicknames of Zongman - Chapter 550

A supreme expert in the Immortal World had died, and a strand of his soul returned to its original body on Earth. Tang Xiu discovered with amazement that ten thousand years passed in the Immortal World, yet only a single year passed on Earth.

Ruthlessly betrayed by his lover and trusted friends, Tang Xiu found that his soul went back to his previous body on Earth, and, despite he spent 10,000 years in the Immortal World, just a year has passed on Earth and many things have changed. Having an unsurpassed knowledge, Tang Xiu will protect his loved ones and go back to the Immortal World to take his revenge.

- Description from Novelupdates

Having transmigrated to a new world and becoming an ordinary Blacksmith in a Blacksmith Shop, Ye Feng shortly has the Master Blacksmith System activated.

Saying 5000 year-old-dragon has an impressive ring to it, yet that dragon was an extremely harmless, herbivorous being. However, because of his uselessly giant figure and scary appearance, he was mistaken for the Demon King’s executive and provided by the nearby village with a sacrificial maiden.

Fundamentally cowardly and timid dragon tried to send her away, but the extremely enthusiastic sacrifice didn’t want to give up. Inevitably, he lied: “Okay, I just ate a small portion of your soul, so you can go back already”, but the maiden with outrageous assumptions has misunderstood that she became the dragon’s kin.

Then, out of all things, she began to manifest strange power on the basis of her wrong assumptions – in turn, the helpless dragon, by some mistake started a rebellion against the Demon King.

Rebellion or whatnot, he wasn’t even his subordinate in the first place.

There’s a legendary Bishoujo Game that has become popular among Japanese gentlemen.