Kanta Senou lives on Shikotan Island with his older brother Junpei, their father Tatsuo, grandfather Genzo, and family helper Mitchan. He is a young Japanese boy with brown eyes and brown hair cut short at ear length.

After Japan's surrender in World War II, Soviet forces occupy Shikotan, abruptly changing daily existence. Kanta and his family lose their home, endure harsh stable living conditions, and suffer food shortages. Amidst this upheaval, Kanta and Junpei meet Tanya, the daughter of the Soviet commander. The brothers adopt names from Kenji Miyazawa’s "Night on the Galactic Railroad," with Kanta becoming "Campanella" and Junpei "Giovanni," reflecting their shared imaginative bond during the occupation.

Kanta frequently cries when facing tension, like the Soviet arrival or family separations, showing emotional vulnerability. Yet, he adapts, learning Russian faster than others and bridging communication with Tanya. His linguistic skill facilitates playful interactions with the Russian children. Despite occasional conflicts from cultural and political divides, the children connect, sharing moments like playing with model trains.

As conditions worsen, Kanta's health deteriorates. The Japanese residents are moved to internment camps in Russia. Learning their father is imprisoned nearby, Kanta and Junpei embark on a symbolic "Galactic Railroad" quest to find him. This journey, mirroring the novel's themes, occurs while Kanta is visibly weakened. His physical frailty contrasts with his steadfast loyalty to his brother and fierce determination to reunite their family.

Kanta embodies childhood resilience amid historical trauma, emphasizing familial bonds and cultural bridges formed in adversity. His story concludes with the brothers surviving their ordeal, marked profoundly by their hardships.