While Cliff, a 27 year old young man, was visiting his grandparents, he was caught in what is called a "summoning" which took him to a forest infested with unknown creatures, he decided that in order to survive, he should be ready to brave all the dangers that would present to him, with his “drain” skill he would fight them to become stronger
Inside the demon base, there was a restless energy. Each demon was busy, preparing for the coming war. They gathered their weapons, shields, and anything else that would aid them because these half-humans had proven themselves resilient—even without the help of the Cursed Serpents. In fact, it was partly due to them that the most powerful demons had not yet shown themselves.
Their leader was hesitant to send out the plague-class fighters, as they were few in number and considered valuable assets. They were meant to face the Cursed Serpent troops when the barrier of lesser half-humans was finally broken. However, these "lesser half-humans" had shown themselves to be far more resilient than expected, growing stronger with each battle.