The Mourning Ceremony. It's a story that repeats every 20 years somewhere in Lapan, a country that is lying on the surface of a large planet called Yerth.
Usually, this phenomenon takes place in high schools, forests, subway stations, colleges or anywhere where activities of people could be seen across the country and nobody knows what triggers it. Even it's so unnoticeable that nobody notices it until everyone dies and one stays alive. It's like a game of survival where only one survives and the others die.
And coincidentally, this game or quest has a deep connection with the dungeons from Helsia where gods and demigods take the challenge.
But none of them survives because suddenly turning into a mortal from god confuses them. They either die from accidents or get killed by a person while doing the quest. It takes more than a year to get used to a mortal body but the duration is too long.
