Dimensional Storekeeper - Chapter 6: You’re Not Scamming Us, Right?

What would you do if you could restart your life?

The doomsday fell upon the earth when a dragon coffin sealed under a snow mountain for ages shifted, and the civilization of gods and devils began. The whole universe turned into a fantastic new world where everyone could rise to the top through cultivation. A lucky young boy seized the opportunity, and started his journey to be an overlord in cultivation.

- Description from Novelupdates

When I cleared the final chapter of a game that was a national failure, I became an unnamed side character in it.

A non-standard, unmeasurable, EX rank supporting character.