6 decades books

As the world came to a sudden end from an unknown storm of mist, humans had to adapt by moving underground in tunnels to survive for several decades. As populations regrew, some wanted the ancient treasures that lie above, which those known as "Divers" would take action and fulfill those wishes by returning above to uncover lost antiques. But one day, a rumor of a rumor telling of a way to finally end the mist spreads amongst cities, and divers are called all-around to search for the hope to finally return above. A veteran diver reluctantly accepts the call from an old friend, and undergoes the journey that which a diver must endure...