Genzo Seno, grandfather to Junpei and Kanta Seno, lives with them and their father Tatsuo on Shikotan Island, working as a fisherman deeply connected to the sea and traditional island life. Following Japan's World War II defeat and Soviet occupation, the family is displaced from their home but remains on the island. As Japanese residents face forced evacuation in 1947, Genzo defies the order to board the ship for internment camps, resolving to stay in his homeland defined by the maritime environment. This choice ultimately leads to his death on Shikotan. Years later, during Junpei and Sawako's return visit, his grave is shown on the island, confirming his passing occurred there. The gravesite serves as a place of remembrance alongside Tatsuo and Kanta, marking Genzo's enduring presence and spiritual tie to the island.