Demonheart Defense

Demonheart
Well-known as a precious energy source.
The owner of Demonheart would be considered the King of the underground world.
Whoever controls it, will have the power to control the Seven Elemental Forces.
Unfortunately... You, who honored as the prince but facing the hard reality that your family's Demonheart will be running out soon.
Your dearest father just passed away but it looks like other demon families have kept their eyes on you…