In regards to the MMORPG Cross Reverie, Sakamoto Takuma boasted an overwhelming strength that was enough for him to be called the Demon King by the other players. One day, he gets summoned to another world with his appearance in the game. There, there are two people that insist “I am the real summon master.” Takuma gets slave-turning magic used for summoned beasts cast on him by the girls―

However, the peculiar ability “Magic Reflection” is invoked! The ones that were turned to slaves were the girls!

Takuma was bewildered. He’s the strongest magician but, he doesn’t have any social skills. Panicking, the first words that came out were the ones that he used inside the game role-playing the Demon King?! “I’m amazing you say? Of course I am. I am Diablo… The one feared as the Demon King!”

This is the story the Demon King (acting) that would soon inspire the world and his other world adventure that he plunges through with his absolute strength, raise the curtain!

As the world is in the middle of an industrial revolution, a monster appears that cannot be defeated unless its heart, which is protected by a layer of iron, is pierced. By infecting humans with its bite, the monster can create aggressive and undead creatures known as Kabane. On the island Hinomoto, located in the far east, people have built stations to shelter themselves from these creatures. People access the station, as well as transport wares between them, with the help of a locomotive running on steam, called Hayajiro. Ikoma, a boy who lives in the Aragane station and helps to build Hayajiro, creates his own weapon called Tsuranukizutsu in order to defeat the creatures. One day, as he waits for an opportunity to use his weapon, he meets a girl named Mumei, who is excused from the mandatory Kabane inspection. During the night, Ikuma meets Mumei again as he sees Hayajiro going out of control. The staff on the locomotive has turned into the creatures. The station, now under attack by Kabane, is the opportunity Ikoma has been looking for.

The war is over, and Violet Evergarden needs a job. Scarred and emotionless, she takes a job as a letter writer to understand herself and her past.