Tensei Shita Moto Dorei, Saikyou no Kizoku ni Natte Toshiue no Musume to Sekai Saikyou wo Mezashimasu summary:
Louis, a fighter who fights slaves in the stadium. Finally loses his life in the match one day. However, the next time he opens his eyes he finds himself in a gorgeous mansion. Louis is reincarnated as the sixth son of a nobleman! And one day after more than a decade has passed, Sharon, a fellow slave from his previous life, appears in front of him. Sharon, who was a child in his previous life, has grown into an adult woman older than him――!?