Demonion ~Maou no Chika Yousai

Once upon a time, there was a demon lord who invaded the kingdom of humans and led the world into war. However, the Demon King's power was taken away by the heroes and sealed deep underground. This is an underground labyrinth where the Demon King is sealed in the deepest part. Due to recent tectonic movements, the seal has been broken, and rumors have spread throughout the kingdom that the Demon King has been resurrected. To subjugate the Demon King and gain fame Skilled adventurers from all over the country visit the underground labyrinth. However, the Demon King uses his magical power to set traps in the labyrinth, summon monsters, and wait for them. The kingdom was thus once again embroiled in war.....