Musou no Kaitaishi

Dungeons suddenly appeared all over the world.
People became “explorers,” diving into these dungeons to obtain resources that could only be found within them!
Sakuto Kurose, too, ventured into the dungeons in search of the “Elixir,” a cure-all medicine, in a desperate effort to save his childhood friend who was afflicted with an incurable disease.
However, he was dismissed by his comrades as being no longer useful in battle—.
Set against the backdrop of both the dungeons and the real world, he faces off against monsters and malicious humans. Thus begins a thrilling otherworldly battle-action!