Martial King's Retired Life - Chapter 109Book 14:

“Why does no one remember the true world?!”

The low-ranking behemoth, the iron mountain is invincible in the horizontal push, and it is called the king of the backing.

- Description from novelbuddy

William and his college class are ripped from Earth and thrown into Aethel, a world on the brink of collapse. Everyone gains incredible magical powers – except William. Mocked and underestimated, he’s an outcast among heroes. But William has a secret: an SSS-ranked skill that lets him travel to Aethel’s past. Learning lost magic from ancient masters, he’ll surpass his classmates and become the true savior Aethel needs. But can he overcome the dangers of the past and present to forge his own destiny? While others studied about the first mage, William could go back in time and see the first mage himself! While others dreamed of seeing a dragon, William could go back in time, hatch a legendary dragon egg and turn it into his puppy. While others used common materials to craft their items, William could go back in time and mine materials that weren’t find anywhere in Aethel anymore. Is it unfair? Perhaps, but William was not the type of person to not use the powers the universe gave him.

Suddenly a high school student Subaru Natsuki has been summoned to another world on the way back from the convenience store. With the biggest crisis of his life being summoned to another world and no sign of the one who summoned him things become worse when he is attacked.