Description from GTL:
Ars, the prince of the Kingdom of Karitz, who was called the strongest wizard, died at a young age. But on the verge of death, he uses reincarnation magic. Reincarnated as Wals Sai, a slave with the best body! Wals, who became the escort of a princess in a small country, became a matchless slave who used her best body and magic to crush all enemies! From "Become a Novelist"! A fantasy adventure by "the strongest slave", opening !! * "Become a novelist" is a registered trademark of Hina Project Co., Ltd.