Masato  

A young boy who has lived for 800 years with an angelic appearance but the soul of Satan. Masato gave mermaid flesh to a woman, posing as his mother until she became useless. Despite appearing childlike, eight centuries of loneliness and wandering have transformed him into a heartless monster. His current "mother," Misa, actually named him Masato after finding her during World War II when she lost her real son in an air raid. Sixty years later, Mana and Yuta discovered Misa and Masato, leading to Masato's desire to make Mana his new mother figure. He drove off in a car and crashed into a truck but it is implied that he continues searching for another mother figure.