Ryu Manatsu (真夏竜, Manatsu Ryū; born April 18, 1950 in Yokohama) is a Japanese actor, singer and voice actor perhaps best known for his role as Gen Ohtori/Ultraman Leo in the Ultraman Series. He performed the show's theme song heard in the first 13 episodes as well.
Source: “Ryū Manatsu”, English Wikipedia (CC BY-SA 4.0), excerpt