In 2034, the doomsday finally comes. People’s concerns have become reality – environmental pollution, extreme weather, exhausted natural resources, virus infection… In a deserted underground urban railway of Walser City, some unknown creatures infected by virus are found. To eliminate those creatures, the government establishes an action team made of prisoners carefully selected. If the prisoners successfully eliminate the unknown creatures, they can be free again. Otherwise, they will get infected by those creatures and die. This action is called “Actiond Expiation”. The team is about to ride on a gas-driven boat to the flooded underground urban railway. The tough fight will soon begin…