Jukokuin no Tensei Boukensha: Saikyou Kensha, Jiyuu ni Ikiru

The great sage, Grameos, tired of his current life as a famous mage, decided to reincarnate as a young boy 200 years in the future. Before reincarnating, he places two magic restraint seals on his hands, so that he can hide his enormous magical power after he is reborn.

His motto for the next life is "Hide my powers, don't stand out, and be free".