MTL - Pokemon Dark Giant - ~ what

Leon, a man who tragically died of exhaustion due to his sister's otome game, unexpectedly finds himself reincarnated as a young aristocrat named Leon Bartfort. However, he soon realizes that he is not alone in this body. Another mysterious entity already resides there, its voice echoing in his mind.Who is this second consciousness? Is it a friend, an enemy, or something far more sinister? Will they be able to come to an agreement to share control over the body, or will a fierce struggle for dominance ensue? Or perhaps their interactions will lead to unforeseen consequences?Intrigued? Then start reading!

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.

When I died I meet with this being who offered me a new chance at life, to actually become someone important and I agreed and was reborn as none other as the First Man.But to think that everything that I ever knew was nothing more than a lie, what am I going to do to survive in such a world?

The world is in ruins. Extreme sub-zero temperatures suffocate the surface, making even simple survival an ordeal. Frozen derelicts of bygone eras span across massive ice wastes. And the survivors closely guard any technology rediscovered within.The only escape from the deadly climate is beneath the surface. But it’s another disaster underground. Monstrous machines lurk in the depths. Unhinged demigods war against them, dying over and over, treating it all like a game. The land itself shifts over time, more contraption than rock. And an ominous prophecy states that the key to everything waits on four heroes - but nobody knows who or where they are.When an expedition into the far uncharted north goes terribly wrong, Keith Winterscar and his father get trapped together in a desperate fight for survival. Stumbling upon an ancient war of titanic scale; the two will need to set their differences aside while they struggle against Gods, legends, and the grand secrets of the realm that lies below.