Kaiji Hamano is a supporting character in the Raimon soccer team, primarily playing as a midfielder. He is recognizable by his sun-tanned skin, navy blue hair that stands up, and a pair of goggles he always wears on his forehead. He typically rolls up the sleeves of his soccer uniform, a small habit that adds to his casual and energetic appearance. His name, particularly the character for sea, is a direct reference to his deep connection with water and his primary hobby.

In terms of personality, Hamano is best described as the cheerful mood maker of the team. He possesses a relaxed and positive outlook, always trying to lift the spirits of those around him. This optimistic nature is a defining trait, making him a supportive and encouraging friend to his teammates. He is especially close to his fellow second-year student, Hayami Tsurumasa, and is often seen spending time with him, whether on the soccer field or engaging in their shared pastime of fishing. Despite his happy-go-lucky demeanor, Hamano is not reckless. He carefully considers his actions and their consequences; his early hesitation to openly rebel against the powerful Fifth Sector came from a deep-seated fear of being forbidden from playing soccer, revealing how much he truly loves the sport. He also has a playful side and enjoys teasing his teammate Midori, though he is quick to backtrack when she reacts violently.

Hamano's journey in the story sees him evolve from a cautious follower to a passionate revolutionary. Initially not as determined as some of his peers to fight against Fifth Sector's oppressive regime, he experiences a significant change of heart during a critical match. From that point forward, he becomes fully committed to the rebellion, his initial hesitation replaced by infectious enthusiasm for the revolution. He later participates in the battles against El Dorado in the Chrono Stone arc. During this period, he volunteers to replace injured players, showcasing his caring nature, but is ultimately forced to leave the team after a severe injury. He, along with many others, is later brainwashed into quitting soccer. In this altered state, his core personality remains relaxed, but his passion for the sport is completely gone, replaced by disinterest. He returns to normal after his team defeats the opposing force.

His key relationships center on his friendship with Hayami, whom he supports and celebrates during matches. He also forms positive bonds with other second-year students like Aoyama and Ichino. He holds a great deal of admiration for the legendary player Tsunami Jousuke, who shares his affinity for the sea. Hamano's most notable ability on the field is his hissatsu technique, Naminori Piero. This move allows him to conjure a small whirlpool around the soccer ball, using it to surf past his opponents with ease, a skill that perfectly reflects his love for the ocean.