Supreme Uprising - Chapter 2: Take Your Medicine

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Growing up in an orphanage and surrounded by poverty, Leo never expected anything good from life. Everyone around him had abandoned him, forcing him to survive as a thief. Yet, fate had other plans.Caught by mysterious figures during a daring theft, Leo is forced into accepting a perilous mission. Transported to a strange, magical world, he confronts terrifying myths he had never believed were real.Suddenly thrust into a brutal, nightmarish battle, Leo hears a feminine voice, filled with authority and danger:“Are you worthy to be my Master?”In that moment, his life changes irrevocably—transformed in ways he'd never dreamed.And the cruellest twist?He's the only human participant in this deadly game. With just one champion at his side, Leo must navigate and survive the merciless battles ahead, relying on his skills to fight, endure, and above all… to steal.But remember, this is just F—

Waking up, I discovered that I had become a cat with superpowers...

Trying to hit on Shinobu mommy.