Genzô Senô is the elderly grandfather of Junpei and Kanta Senô, living with them on Shikotan Island. He has spent his entire life on the island, embodying a deep connection to its traditions and way of life through his work as a fisherman. This lifelong bond with the sea and island shapes his identity and actions.

Following Japan's surrender in World War II and the Soviet occupation of Shikotan, Genzô demonstrates immediate defiance against the invading forces. When Soviet soldiers enter his home armed, he confronts them directly, demanding they leave despite the threat they pose, underscoring his unwavering commitment to his home and refusal to yield.

As the occupation intensifies, the Japanese residents, including Genzô's family, are forcibly relocated from their homes for Soviet families. During this upheaval, Genzô maintains his steadfast attachment to Shikotan. When the Japanese population is ordered to evacuate the island entirely for deportation to internment camps, he categorically refuses to leave. He declares his intention to remain, choosing to live out his final days fishing in the surrounding waters.

His decision to stay is an act of resistance and profound expression of his identity. He resolves to die as he lived, on his boat surrounded by the sea he cherishes. This final choice positions him as a symbol of the island's enduring spirit and the deep loss experienced by displaced residents who could never return.