Ian Percus, the second son of a countryside Viscountcy.
One day, he received a love letter from the future.
'If we don't protect the future, the world will perish.'
With an ominous warning scribbled by someone

aCompared to our time, the current generation just arenat as reliablea they said, aStill, isnat he the son of the Hero?a How annoying.
Itas been over ten years since the battle between mankind and the demons ended. The children of the heroes who saved the world are all grown up.
One of them, Earth, was a talented man, and everyone expected him to succeed his father as a warrior and defend his country, but Earth was always wary of his fatheras title.
One day, Earth is shocked to find his fatheras sword, which was used to overthrow the Demon King, sealed in his familyas mansion.
Because trapped within was the ghost of the Great Demon King who was unable to pass on and continued to roam the world.
For some reason, only he could see the spirit of the Demon King, and the Demon King possessed him through the sword.
Every day, forced to coexist with the spirit of the Demon King, they live a strange shared life, when the Demon King whispers to Earth on a whim.
aI have a grudge against your father. If you want to get back at your father and the world, Iall train you. Iam free.a
Earth receives special personal guidance from the Demon King just to get back at his parents and the world.
Then, in the coming days. The heroas parents, the heroes of the past, the first love, the princess childhood friend, the geniuses of the era, and the world will tremble.

A price is always exacted for what fate bestowsaadapted from Zweigas Mary Queen of Scots.
aIam a nobody, with no time to notice the brightness of the sun.
aMy parents couldnat help me, and I wasnat highly educated. I had no choice but to make it on my own in the city.
aIad applied to many jobs, but no one ever hired me. Maybe itas because Iam not good at expressing myself, and Iam not the best communicator. I guess I just havenat shown enough ability.
aOnce, Iad eaten two loaves of bread over a three-day period. Hunger kept me up at night. At least I paid a monthas rent in advance, so I didnat have to face the cold winter wind outside.
aFinally, I found a job at the hospitalas morgue, keeping vigil over the dead.