Ryu Manatsu (真夏竜 Manatsu Ryū) is a Japanese actor, singer and voice actor. His real name is Mikio Seto (瀬戸 幹雄 Seto Mikio). He is best known for his role as Gen Otori/Ultraman Leo. He also sang the theme song for Ultraman Leo and is a member of the Ultraman Foundation.
The filming of Ultraman Leo was a very intense and difficult experience for him, with the training Dan Moroboshi gives Gen proving painful and difficult to enact. During the filming of episode eight, he was paralyzed from the waist down because of a scene in which Gen sits under a waterfall in the freezing cold. 
- Ultraman Leo: Gen Otori/Ultraman Leo (voice)
- Ultraman Max : Unnamed Policeman (Guest Appearance, Episodes 33-34)
- Ultraman Mebius : Gen Otori/Ultraman Leo (voice)
- Mega Monster Battle: Ultra Galaxy Legends The Movie: Ultraman Leo (voice)
- Ultraman Zero The Movie: Super Deciding Fight! The Belial Galactic Empire: Ultraman Leo (voice)
- Ultraman Saga: Gen Otori/Ultraman Leo (voice)
This section here refers to Ryu's grunts being reused per stock footage on other Ultraman Series:
- Ultraman Leo: Ultraseven (low-pitch version) and Astra in grunts
- Ultraman Mebius Gaiden: Hikari Saga: Ultraman Leo in grunts
- Ultraman Ginga: Ultraman Leo in grunts
- Ultraman Geed: Ultraman Leo in grunts and Ultra Capsule
- In episode 3 and 4, although the scene of special training the chop toward the basin is famous, at the time of this shooting is actually in the middle of winter, his lower body had paralyzed past the cold. In the very beginning when Ryu Manatsu are asked your impressions of shooting in Leo also at the time of the magazine, "No, I'm strong in the name exactly as midsummer, but the middle of winter is painful." And enough to comment. Comments made after is so "It was really dying too too cold."
- Even in special training scenes other than the above, Gen Otori of the force of the screen "Jeep special lesson" in episode 6 was not only acting by Ryu, but realistic harshness itself. Special training that confronts opponents with the pointed log with the same story is also a very dangerous scene, but this special scene was full story no stunt. Regarding jeep training, "I confessed in a later interview that I was told that" When I protest that I will be thrown out and die "if there is a photo taken with a sweet braking jeep and saying" Next time " It is.
- Besides the above special training scenes, all the actions of Gen Otori were all handled by Ryu Manatsu himself. Good of the height and the action of the body's ability, even Kohji Moritsugu, the actor who portrayed Dan Moroboshi and Ultraseven's voice actor, was co-starred has acclaimed in his own book.
- Aside from Gen Otori, the only role that Ryu Manatsu played was an unnamed policeman in episode 33 and 34 with the Leo Ring in Ultraman Max.
- Ryu Manatsu has a friendship with Saburo Shinoda, Kotaro Higashi's actor and Ultraman Taro's first voice actor even though Saburo have never co-starred in the Ultraman Series after the end of Ultraman Taro. Their sons are even classmates. When Ryu suffered from gastric cancer in 2004, Saburo cooperated with treatment by introducing a second opinion. However, Tsuburaya Productions is not coupled with co-star-winning deployment of the settings and the contents of the Ultra Brothers in the shooting of.