Jinpei, designated G-4 and codenamed "Jinpei the Swallow," serves as the reconnaissance expert for the Science Ninja Team. He is approximately 10-11 years old during the original series, aging to 13 in the sequel *Gatchaman II*. His height remains consistently documented as 120 cm, with brown hair and dark eyes. Jun discovered him as a toddler on Mount Jupiter, with no knowledge of his biological parents or early life. She brought him to the Shirayuki Orphanage, where they were raised together. Jun named him and designated their meeting day as his birthday, his actual birthdate unknown. Dr. Nambu recruited both after Jinpei showcased exceptional agility and swiftness, traits popular among the orphanage children. Jun insisted they join together or not at all, leading to their mutual adoption by Nambu. Jinpei occasionally claimed descent from the Iga or Jupiter Ninja clans, though this was never definitively confirmed. One theory suggested he might be the sole surviving son of the Jupiter Ninja Clan's sensei, who disappeared around the time Jun found him. In civilian life, Jinpei assists Jun at her establishment, Snack J, handling cooking, dishwashing, and busboy duties. He holds a special driving permit for his dune buggy, preferring discreet use to avoid police attention. His personality blends typical childlike exuberance with unexpected maturity, exhibiting cheerfulness, mischievousness, and a tendency for pranks or foul language, yet also displaying strong responsibility in teamwork and business operations. A recurring trait is his desire to prove his capabilities, often feeling underestimated due to age and size, which occasionally leads him to undertake risky solo missions. He collects stray animals like seals, whales, and mountain lion kittens, though Jun typically prevents him from keeping them. Jinpei's relationships define his familial structure. Jun is his adoptive sister, whom he addresses as "Oneechan" until episode 95 of the original series. He relies on her for comfort despite frequently teasing her about her feelings for Ken. Ken Washio is a brother figure, addressed as "Aniki," whom Jinpei deeply respects as his leader. Jinpei also persistently reminds Ken of his unpaid tab at Snack J. Ryu serves as a comedic partner, while Dr. Nambu and Olga Riddenbacher fulfill parental roles as father and mother figures. Jinpei experiences fleeting maternal connections, like a village woman who mistakes him for her lost son, Jinbei, allowing him temporary experience of motherhood before duty separates them. His civilian attire typically features an orange-and-yellow T-shirt with a "4" insignia and blue-and-white striped bellbottom pants, later updated to a crew-neck shirt, cap, and blue jeans with suspenders in sequels. His Bird Style battle uniform varies: the original series depicts a yellow suit with red gloves/boots and a blue cape with teal interior; the 1994 OVA redesigns it primarily red with yellow accents and a purple cape. Concept art for the canceled Imagi film project experimented with gold and red color schemes and visible seams. Jinpei's weapons evolve. Initially, he employs "American Clackers," bolas capable of restraint or outfitted with blades/explosives. In *Gatchaman II*, he uses the "Rebound Ball," a super-ball projectile launched from a mitt. *Gatchaman Fighter* introduces the "Swallow Top," a spinning top on a yo-yo string. The OVA adds an unnamed hacking device with a collapsible screen and gamepad interface, syncing data to his helmet visor. His fighting style emphasizes stealth and incapacitation, leveraging his small size for agility over direct confrontation. He utilizes feather shuriken issued to the team and participates in combined "Tornado" attacks. His primary vehicle, the G-4 (or Helico-Buggy), is an amphibious armored buggy disguised as a civilian dune buggy. It transforms via his wrist device, enabling land, sea, and air travel with helicopter blades and jet thrusters, featuring equipment like rotating saws, drills, and later a bomb launcher. Maximum speed reaches 200 km/h. In the OVA, it appears as a magenta-and-white buggy that armors upon activation, equipped with flight rockets. Jinpei appears in spin-offs and crossovers. He features in cameos within the *Yatterman* franchise, aiding against antagonists like the Doronbo Gang. In *Time Bokan: Royal Revival*, he appears with the team at Boyacky's restaurant. *Wonderful Tatsunoko Land* includes a brief speaking role. International adaptations alter his character significantly; *Battle of the Planets* reimagines him as "Keyop," a genetically engineered child with a speech impediment, often misinterpreted by fans as censoring profanity. Earlier concepts for this version considered him an alien or android.