MTS: Marvel and Beyond - Chapter 18 - : Two Arc Reactors

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

After many years of unrequited love, she used her power and favors to coerce him into marrying her. Yet, she knew there was a constant “lunar light” in his heart. In the presence of this lunar light, he would never cast a glance upon her. Eventually, she regretted it, she no longer wanted this marriage. But who could tell her why the man had started to relentlessly pursue her now?

Long ago a great calamity struck the earth, destroying much of it and merging what remained with pieces of other worlds.

With these worlds came Aether, a new form of energy that can allow one to transcend the bounds of normal mortality and human limitations.

In a world where humans absorb the essence of aether beasts to gain power, Aiden Hawke joins the class of humans known as arcanists, people who defeat aether beasts and absorb their essence into cores they forge within themselves, and who infuse themselves with the aether that permeates the world around them to increase the power of their body and mind.

However, unlike most, Aiden will find that he holds a unique gift and that his journey as an arcanist will not be so simple.

In a romance novel called “The Secret Lovers of the Academy” the male lead would often torment his fiancée–but wait, why did she cross into this world to become his fiancée, the villainess, instead of the heroine?