DxD: I Steal Luck - Chapter 115: The Awakening of the Sacred Gear!

A story of time-travel. Sly and cunning, she unexpectedly became a sickly noble lady whose fiancé is merciless and demotes her to a lowly concubine. She sneers and bravely breaks off the engagement. To hell with scumbags, marry heirs to lords, blind the courts with her brilliance.

Heed my call! O’ Dragon of Eternal Sin, the Progressive Disaster, the Forerunner, the Land of Eternal Peace, the Flames of Soul Burning, He Who Owns The Deep Soul, the Sound of Origin, the First Cause of All Things, the Principle of Circles… o’ great Negary, your servant calls for your return!

“I’m sure we’ve all had that weird kid in our class.”“You know, the one everyone avoids like the plague.”“The moron who always comes to school with messy black hair, torn-up clothes, and so many bruises on their body it looks like they were mauled by a bear.”“I know that kid well—”“Because I’m him.”[DING!][YOU HAVE AWAKENED YOUR BLACKSMITH SYSTEM]“Blacksmith system? What the fuck is that?”It’s the power to forge.The power to create weapons that can split the heavens themselves.Weapons that can challenge gods, rewrite fate, and reduce galaxies to dust.Weapons that can cut through time and space.With the Blacksmith System… you have the power of creation.Do you accept?[Y/N]

A failed investor from 2017 got drunk and woke up in the 1980s. China is just opening up, and the economy is blooming. There is also the dissolution of the Soviet Union, the bursting of the Dot-com bubble and other financial crisis. He used his knowledge of the future and slowly build up his empire.