Ryu Nakanishi, codenamed the Horned Owl and designated G-5, pilots the Science Ninja Team's vehicles as their primary operator. Hailing from a small fishing village, his father Matsuzo and younger brother Seiji maintain their seafaring livelihood. At age 13, Ryu rescued Dr. Nambu from a whirlpool, an act that leveraged his oceanic mastery to secure his place as one of the team’s final recruits. In the OVA continuity, his heritage shifts to half-Japanese and half-Aboriginal Australian, with upbringing near the Great Barrier Reef and training in ocean rescue programs. Ryu possesses a heavily-built, muscular physique reminiscent of a sumo wrestler, standing 170 cm tall and weighing 80 kg. His civilian attire typically includes a green shirt marked "5" and khaki pants. In Bird Style, his suit is predominantly brown with a green cape featuring deep red trim, an orange-beaked helmet, and lavender visor. The OVA redesign grants him deeply tanned skin, a blond mohawk with purple sides, and a gold-accented deep green suit. Concept art for the canceled Imagi film project alternated between a bulkier armored suit and a sleeker green-and-gold version. Personality blends laid-back optimism with flashes of arrogance and volatile temper when provoked. He exhibits strong empathy toward teammates and civilians, counterbalancing more cynical members like Joe. Boredom often drives him to nap during downtime at the yacht harbor he manages—a cover for storing the God Phoenix. Despite reluctance toward non-pilot duties, he remains unwaveringly loyal to the team. Ryu demonstrates unparalleled skill maneuvering the God Phoenix through complex aerial and underwater operations. His combat style emphasizes brute force, overpowering foes through body-slams or grappling entire ships. His arsenal includes a Harpoon Gun for ranged attacks, the elastic Gripper rope in *Gatchaman II*, and the Owl Sickle kusarigama in *Gatchaman Fighter*. He also operates mechas like the amphibious Horned Tank and bulldozer-inspired Gatcha Five, which integrates into the Gatchaspartan’s engine and rear assembly. Character development intensifies in *Gatchaman II* when Galactor abducts his father and brother to exploit his loyalties. Infiltrating a disguised Galactor tanker for their rescue, Ryu emotionally fractures when his father refuses to act as bait against him. Though the team aids the mission, Ryu’s identity as G-5 stays concealed from his family in the original Japanese version—they believe he merely subcontracts for the team. His interactions with the resurrected cyborg Joe underscore themes of loyalty and acceptance. Beyond the main series, Ryu battles the Doronbo Gang in *Yatterman (2008)* and abandons a fight out of boredom in *Time Bokan: Royal Revival (1994)*. International adaptations include South Korea’s *Eagle 5 Brothers* (renamed Yongmin or Yong) and *Battle of the Planets* (recast as "Tiny Harper," using his size for ironic humor).