MTL - Master of Ninja World - v16 Chapter 27 explain

Alvin had planned his future: after leaving the city of Serinthia and obtaining his graduation certificate in technology, he would return to his hometown, stay close to the only girl in his life, and kill a few people from time to time for fun and entertainment.But fate had other plans. On an ordinary day in the Royce Empire—one of the three great empires that ruled this world—the sky split open and a barrage of meteors descended. From that moment, the world changed, and the lands of the empire turned into a battlefield, as monsters appeared and people became hunters.Now, Alvin found himself forced to abandon his former dreams and return to his city before the companion of his life dies.

An ultimate warrior, the one and only Alchemy Emperor, Ling Han, died in his quest to achieve godhood. Ten thousands years later, he, with the ‘Invincible Heaven Scroll’, was reborn in the body of a young man with the same name. From then on, winds and clouds moved as he set himself against the uncountable geniuses of this new era. His path of becoming a legend has begun once more. Of all eras underneath the heavens, I am the strongest!

- Description from Novelupdates

Sam Sanderson is envied by many for his job, however he himself didn't seem to like it much.

Due to his expertise in nanotechnology he was tasked with monitoring the state the Valkyries, humanity's strongest weapons who all just happen to be made into gorgeous females.

Forbidden from even touching any of them, Sam spends his days in agony watching flowers he couldn't hope to touch. However one day all of that seemed to change.

Side story of Kyoukai Senjou no Horizon bundled with the first press release of the 1st, 3rd, 5th and 7th Blu-ray volumes of both seasons of anime.

This side story follows Asama, Kimi and Mitotsudaira aboard Musashi one year before the beginning of the main story, as Asama is considering to create a music band together with her two friends for the next festival in Aki, a territory under the governance of K.P.A. Italia.