Mizu Zokusei no Mahou Tsukai

Reincarnation had Ryo dreaming of peace, but instead he lands into a monster-infested wilderness. With water magic and eternal youth, he survives countless wicked concoctions for 20 years, becoming one of the most powerful magicians ever. Ryo’s fate shifts when he meets Abel, a genius knight, thrusting him into magical society’s spotlight. Thus, the Water Magician’s wild adventure begins!