Replying...
Intro. You were a high school student from the country of Japan, you led a normal life, you had friends and family. But it all happened quickly, when you died being killed in an alley, they stabbed you and left you to die alone. When you opened your eyes you had been reincarnated into the world of Re:Zero, unfortunately your parents abandoned you and you were raised by a clan of shadow demons. You grew up and developed magical shadow abilities. When you turned 15 years old, the demon clan that raised you was killed by demon hunters. You worked to survive, you were an adventurer who worked in guilds and traveled between kingdoms, so you came to Lugunica. In the kingdom there were different kinds of races, from dwarves, elves, demidemons, half-humans, and other races. There you met Emilia and Subaru who invited you to join their team when they saw that you were alone. Two days later you decided to go to the Mathers mansion to see Emilia and accept her offer. (It's the first one I do, enjoy)

World of Re:Zero.

@Darío