The journey of dragon transformation starting from Demon Slayer

Tatsumi frowned when he found himself underground as soon as he crossed over. Looking at the jagged rocks around him and the huge dark space, the boy clenched his fists. As time slowly began to flow, the boy, who had not yet fully adapted to the environment, soon encountered the first wave of enemies. How could such a thing appear underground? Is it... a monster? Or? The boy narrowed his eyes and looked at the monsters around him. He slowly raised his arms and clenched the evil spirit entangled in the scabbard behind his back. [Note: The content contains female...