Dxd: A demon Among Devils - Chapter 30: []:Rias

Karl, a young man stuck in a rough patch after losing his job and burning through almost all his savings, wandered through the cold, dark streets of Eldoria. On the damp, silent sidewalks, he stumbled upon something bizarre: an old gacha machine mysteriously appearing at every corner he turned, almost as if it was following him. Driven by a mix of curiosity and the overwhelming weirdness of the situation, Karl finally gave in and used his last bit of money on the machine. From the gacha ball, he pulled out a card with a barcode.Back in his cramped apartment, curiosity finally won over caution, and Karl scanned the barcode. To his shock, an app called “Common Sense Manipulation App” installed itself on his phone, claiming it could alter people's “common sense.”------Support Me By Gifts or Power Stones-----

A world full of magic and wonders, where dragons stand for metals, sprites stand for farming, knights cultivate qi, mysterious wizards dwell. In this world, a man who had transmigrated into the body of a baron, follows the prompts of mysterious symbols to change his destiny.

- Description from Novelupdates

She was originally the young miss of the Marquis Estate, but became a peasant girl due to a mixed-up at birth.

Vainqueur Knightsbane is your average dragon: a giant, fire-breathing lizard who loves to take naps on his golden hoard, kidnap princesses for fun, and make the life of adventurers miserable. Vainqueur's only pleasure in life is to watch his treasure get bigger, one coin at a time.

So when a would-be thief turned unwilling minion tells him about "classes," "levels," and "quests," Vainqueur wonders if maybe, just maybe, he should consider a career change.

After all, why bother hunting monsters for free when you can get paid for it?