Reincarnated as the Baron's son: My Infinite Card Upgrade System - Chapter 20: Negative relationship.

"God of Mischief is interested in you and wants you to be his emissary. Do you accept?"

With blood and wounds covered his entire body, the voice echoing inside his mind was like that of a hope shining upon him.

In the glorious future era, mankind had discovered the bottom of the sea and conquered the sky, but they also accidentally opened the Pandora box that shouldn't be opened. They found a place where lived numerous unknown creatures.

Here, humans will wrest their lives to step upon their greatest evolution and create their own myths, including Theodore.

Faced with betrayals, surrounded by beasts, and faced with imminent death, he answered with resolve and tenacity.

"Yes!"

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Arnold never thought his gaming skills would land him in a romance novel—as a doomed side character, no less. To survive, he hijacks the heroine's “system,” bending the story to his will. But when he dodges a deadly duel, he catches the eye of the heroine, Lara, his own step sister—and her love is a dangerous game. Arnold must outwit the plot and his step sister who's not afraid to kill for love. In this LitRPG romance gone wrong, survival isn't just about beating the system—it's about escaping the heart of a yandere.