Zero no Tsukaima - Volume 20 epilogue

Everyone wants superpowers, including Alden Thorn.But even if he's lucky enough to be one of the few humans granted magical abilities by the extraterrestrial System that's been running things on Earth for decades, his goal of being a battlefield support hero is still a long way off.He's got determination on his side and maybe a murderous alien desk clerk, too.The universe is a complicated place. Alden's about to meet it.

This novel is also known as From The Start, I Traded A Galactic Warship

After getting a trading platform three thousand years later, everything in the world has become an antique, worth a thousand gold.

But it was also learned that three years later, aliens invaded, human beings fell, and the dark starry era began.

In this era of unprecedented change in tens of thousands of years.

Shen Shi decided.

First trade a space battleship, and then talk about it.

then–

Battleships come to the world from outer space! Global shock! Starry Sky Era, open in advance!

- Description from novelbuddy

Upon meeting the girl who would become her adopted younger sister, the duke’s daughter Christina regained memories of her previous life. Through those memories, she learned that her new sister, Mishuli, was the heroine of a certain story. And though the story depicted a Christina who abused her sister, the real Christina turned into a siscon who spoiled Mishuli to no end.