Jinpei, designated G-4 and known as the Swallow, serves as the reconnaissance expert for the Science Ninja Team. He is the youngest member, approximately 10-11 years old during the original series and 13 in *Gatchaman II*. Orphaned at a young age with no knowledge of his parents, Jun discovered him as a toddler in the Jupiter Mountains while fleeing a war that killed her own parents. She brought him to the Shirayuki Orphanage, named him Jinpei, and raised him as her adoptive brother, establishing the day she found him as his birthday. Jinpei claims descent from the 18th generation of the Iga Ninja clan, though this remains unverified. An implication exists that he may be the sole surviving son of the Jupiter Ninja Clan’s sensei, who disappeared around the time Jun found him, with the connection remaining unexplored. Dr. Nambu initially sought to recruit only Jinpei for the team, drawn by the child's popularity, nimbleness, and mischievous orphanage pranks. Jun insisted they not be separated, securing her own inclusion. During non-mission hours, Jinpei assists Jun in operating her establishment, Snack J. Physically, Jinpei has brown hair, black eyes, stands 120 cm tall, and weighs 30 kg. His typical civilian attire features an orange-and-yellow T-shirt marked with the number "4" and blue-and-white striped bellbottom pants. By *Gatchaman II*, his clothing updates to a crew-neck "4" shirt, cap, blue jeans, and suspenders. His Swallow-themed Bird Style uniform is primarily yellow with red gloves and boots, a dark blue cape (teal-lined), and a blue helmet with a yellow visor in the original series. This design shifts to primarily red with yellow accents and a purple cape in the OVA. Concept art for unproduced adaptations, like the Imagi film, experimented with gold and red color schemes. Jinpei exhibits a cheerful, excitable, and mischievous personality. He serves as the team’s "idea man" and shares a comic relief role with Ryu. Despite his playfulness, he demonstrates responsibility through his work at Snack J and steadfast mission support. He dislikes academic subjects like math but enjoys drawing and card games. His closest bond is with Jun, whom he teases about her feelings for Ken yet deeply respects as a sister. He views Ken as an older brother, addressing him as "Aniki" and respecting his leadership, though he unsuccessfully prods Ken to settle his snack bar tabs. As reconnaissance specialist, Jinpei’s fighting style emphasizes stealth and incapacitation, compensating for his stature. His signature weapons evolve: American Clackers (bolas) in the original series, a Rebound Ball projectile in *Gatchaman II*, and a Swallow Top (yo-yo-like spinning top) in *Gatchaman Fighter*. The OVA replaces these with a hacking device featuring a collapsible screen and gamepad interface, syncing data to his helmet visor. His vehicles include the Swallow Helico VTOL recon aircraft and the tank-like Gatcha Four from *Gatchaman Fighter*, which forms part of the combined mecha Gatcha Spartan. Jinpei’s character development across official media maintains core traits while adapting to new contexts. The OVA modernizes his skills, depicting him as a computer-educated hacker and gamer. His role as the youthful, agile scout persists. Later sequels show maturation—his *Gatchaman II* design reflects slight aging, and his weaponry becomes more sophisticated—though his energetic, loyal personality endures. Unproduced projects, like the Imagi film, explored updated uniform designs without altering his fundamental backstory or characteristics.