Kinro is a young man from Ishigami Village, the older brother of Ginro. Both brothers serve as the village gatekeepers, tasked with enforcing rules and protecting against outsiders. He maintains staunch seriousness, deeply committed to order and regulations, often declaring rules must be upheld regardless of circumstances. This strict adherence fuels his initial suspicion towards Senku Ishigami and Chrome, whom he perceives as threats due to their use of "sorcery" (later understood as science). He physically blocks their entry, refusing compromise. His dedication to duty remains unwavering. He reprimands Ginro for neglecting guard duties or susceptibility to bribes, emphasizing their role's importance. Even when tempted by Senku's creations, like the gold-plated spear crafted to match his name, Kinro initially insists no offering can sway him, though he secretly admires the spear and refuses to part with it. This spear is later destroyed when Kohaku uses it as a lightning rod during Gen Asagiri's arrival. Kinro secretly battles severe nearsightedness, known in the village as "blurry eye sickness." He considers this a personal failing and actively conceals it, believing a man should make no excuses. This disability severely hampers his combat effectiveness, especially in close quarters, despite being one of the village's most skilled spear users. His vision problems become critical during the village games against Magma. Initially holding his own, Kinro struggles as his vision blurs, leaving him vulnerable to missed strikes. Suika recognizes the issue and throws him her watermelon helmet containing makeshift lenses. With vision temporarily corrected, Kinro's true skill emerges, overwhelming Magma until a surprise attack knocks him out. Following this, Senku provides him with properly crafted glasses. Accepting these glasses resolves his vision impairment, allowing him to fight at full potential. He acknowledges the value of the "eyes of science." Equipped with glasses, Kinro becomes a more reliable and formidable warrior for the Kingdom of Science. He participates in defending the village against Hyoga and the Tsukasa Empire's invasion. During the bridge battle, despite being wounded by Hyoga, he tenaciously holds on, ordering Ginro to destroy the bridge if necessary to protect the village. He survives thanks to Senku's intervention and receives medical treatment. Kinro continues as a key member of the village's warrior team. He later joins the crew of the science vessel Perseus on its voyage to locate the source of the petrification device, exploring the "New World." His relationship with his younger brother Ginro features constant friction, Kinro's sternness contrasting with Ginro's laxity. Despite this, a deep bond exists. Kinro is visibly horrified when Ginro nearly falls during the Hyoga attack, and Ginro refuses to cut the bridge while Kinro clings to it. Kinro later reassures a panicking Ginro about his wounds. His trust in Senku and science grows substantially. Initially dismissive of science's combat value, witnessing Senku's explanations and inventions, particularly the solution to his vision, changes his perspective. He actively vouches for Senku's character and intentions to village elders like Kokuyo, first supporting Senku's bid for leadership and later advocating for him to treat Ruri, stating his belief in Senku and science. After the main storyline concludes, he accepts a role maintaining order by becoming a police officer.