Tensei Shita Moto Dorei, Saikyou no Kizoku ni Natte Toshiue no Musume to Sekai Saikyou wo Mezashimasu

The arena—a place where slaves are forced to fight to death. Lewis was one such slave who lost his life in a match. But when he opened his eyes again, he found himself in the garden of a luxurious mansion. Much to his surprise, Lewis reincarnated as the sixth son of a nobleman. One day, more than ten years after his reincarnation, Lewis meets a fellow slave and friend from his previous life, Sharon. But while Lewis knew Sharon as child, she now appears in front of him as a lady older than Lewis himself. (Source: Manga UP!)