Jinpei, designated G-4 and known as the Swallow, is the youngest member and reconnaissance expert of the Science Ninja Team. Little is known about his early life. He was discovered as a toddler by Jun in the Jupiter Mountains after she fled there to escape a war that killed her parents. Jun brought him to the Shirayuki Orphanage, where they were raised together as adoptive siblings. Jinpei claims descent from the Iga Ninja clan, and it is implied, though never fully explored, that he might be the missing son of the Jupiter Ninja Clan's sensei, who vanished around the time Jun found him. Dr. Nambu initially planned to recruit only Jun, but she insisted they stay together, resulting in their joint training under his guidance. Typically cheerful, excitable, and mischievous, Jinpei also shows responsibility by helping Jun run her snack bar and supporting teammates on missions. He serves as the team's "idea man" and shares comic relief duties with Ryu. He enjoys playing cards and drawing, but dislikes math and homework, which Dr. Nambu oversees. Ken is a respected older brother figure Jinpei calls "Aniki," though Jinpei often teases him about unpaid snack bar tabs. His bond with Jun is especially strong; he assists her daily and sometimes needles her about her feelings for Ken. Jinpei stands 120 cm (approx. 4'7") and weighs 30 kg, with brown hair and black eyes. His civilian outfit is typically an orange-and-yellow T-shirt with a "4" and blue-and-white striped bellbottoms. Later sequels update this to a crew-neck "4" shirt, cap, blue jeans, and matching suspenders. His original Bird Style Swallow uniform is primarily yellow with red gloves and boots, a teal-lined dark blue cape, and a blue helmet with a yellow visor. The 1994 OVA changes his Bird Style to red-dominated with yellow accents and a purple cape. Unproduced adaptations featured redesigns: the cancelled Imagi film experimented with gold-and-red color schemes and 3D emblems, while the 1998 New Gatchaman reboot envisioned a modern casual look with a navy hoodie, yellow shirt, gym shorts, and sneakers. As reconnaissance specialist, Jinpei's combat style emphasizes stealth and incapacitation, compensating for his size against adults. His signature weapons evolve: the original series features American Clackers (bolas for restraint), Gatchaman II introduces the Rebound Ball (a super-ball projectile launched from a mitt), and Gatchaman Fighter gives him the Swallow Top, a spinning top on a yo-yo string. The 1994 OVA equips him with a hacking device featuring a collapsible screen and gamepad, syncing data to his helmet visor. His primary vehicle is the G-4 (Helico Buggy), an amphibious buggy transforming into the VTOL Swallow Helico for reconnaissance. It travels at 200 km/h on land, sprouts helicopter blades for flight, seals its cockpit underwater, and later gains bomb-launching capabilities. Jinpei's portrayal varies in adaptations. Battle of the Planets renames him Keyop, reimagining him as a genetically engineered child with a speech impediment linked to defective "cerebonic implants" or artificial origins. G-Force: Guardians of Space restores his name but keeps the artificial-life backstory. The 1994 OVA interprets him as an internet-educated prodigy skilled in hacking and gaming, aligning with the New Gatchaman reboot's concept of him as a computer genius. He also appears in crossover media like Yatterman (2008) and Time Bokan: Royal Revival (1994), though these are brief cameos without substantive development.