One day, the world was suddenly overrun by monsters straight out of a game. Office worker Shuichi Sato was shocked by the situation, yet deep inside, he felt an uncontrollable excitement burning within him. Upon acquiring a mysterious skill called "Monster Encyclopedia," he realized his true desire— "I must register every single monster in existence!" Yes, Shuichi was a completionist at heart… and now, in this monster-infested world, his obsession has become his greatest weapon! An adventure-packed fantasy where a salaryman turns his encyclopedic passion into the ultimate survival skill!