Harry Potter: Eclipse. - Chapter 2:

The empire has turned into the land of the undead due to a spell gone wrong. God summoned heroes from countless worlds to purify the empire and plant new hope. Lee Shin Woo, an ordinary earthling, was also summoned. As an undead, that is.

He said I was the most despicable woman he ever met…

In order to love him, I lost my family, and become an imprisoned tool used for his vengeance from a noble lady. Everyone said I was the daughter of a rapist… I cautiously maintained the excruciating deep love for him and suffered from mental and physical exhaustion…

I thought someday my love would touch him and then I would live a happy life just as a fairy tale, but in fact I fell into an eternal nightmare…

Liola—the best assassin in his world—has vowed to kill no more. He was being chased by an assassination organization when he accidentally dropped into a parallel universe: through a dimensional gate and into poor teenager Kaiser’s apartment. Instead of going to the government shelter for lost dimensional travelers, Liola and Kaiser wind up going to school together.

Liola has been trying his best to live the life of an ordinary person, but after certain things happen one after the other, he begins to realize that being an ordinary person could be harder than being an assassin.