Subsistence and solidarity

The year is 2042, and the surface is uninhabitable due to the radioactive fallout and debris that still litter modern day Tokyo due to the all out nuclear annihilation that has plagued the earth since 2039, Kato Soryu the main protagonist believes he is the only person left alive after years of searching for any form of human life he has lost all hope, he has survived by living in the metro system of Tokyo and struggles to survive having to make trips to the surface to get food, water, and other necessities, however his supply of oxygen is wavering and his will to live is reduced to nearly nothing due to the pure loneliness of his situation, until one day during a run to the surface for cigarettes to cope with his nicotine withdrawal, by chance he stumbles upon another living soul in a grave situation.