Starting out as a Dragon Slave

When Isaac opens his eyes, it\'s not death that awaits him, but a new life... in a world identical to his own, with one exception: portals leading to monster-infested dungeons are appearing across the globe. If their boss isn\'t defeated in three days, the creatures escape and wreak havoc.
In this world, awakened hunters are the only line of defence against these horrors. Graded from F to SS according to their magical power, they rule in a society dominated by force. Isaac wakes up in the body of a young boy of rank F, an orphan with no future.
But his destiny changes when he discovers a unique gift: every night, his mind is projected into another world, a nightmare where dragons have enslaved humanity. In this hell, he is just another slave... but he soon realises that this cursed world holds the answers to the future of his own.
To survive and prevent history repeating itself, Isaac must move forward. His only hope? A mysterious system that allows him to absorb the strength of his enemies. Armed with a katana, he embarks on a race against time to unlock the secrets of these two worlds and prevent the inevitable.