[World Setting Knowledge]

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  Souls

When a person dies, they turn into a soul. They cannot interact with physical objects and are invisible to living people. They can feel emotions. Souls can make physical contact with other souls.

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  Grim Reapers

These are souls paying for their karma from life, or souls who volunteered to become Reapers. Nagumo belongs to the former.

White butterflies always fly around a Grim Reaper. They often wear suits. (Black hanboks are old-fashioned...)

A Grim Reaper's weapon is generally a gun or a knife. To a Grim Reaper, a Specter is like an ant. There is an overwhelming difference in power.

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  Specters (怪異)

Monsters that souls eventually turn into if they stay in the human world for too long. They vary in size and shape. Some are disgustingly huge, while others are monsters with many limbs.

A soul that was pure white gradually becomes murky and turns into a Specter once it becomes completely black.

Once they become a Specter, they lose their reason and exist only on instinct, devouring souls. They bite souls and drain them. Killing Specters is one of the Grim Reaper's duties.

If bitten by a Specter, the bitten area turns black and gives birth to another Specter.

Solution: Go to the Afterlife before turning completely black. (Once a soul has fully become a Specter, going to the Afterlife is useless.)

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  Duty of a Grim Reaper

Once assigned a soul, the Reaper must live with them in their house until the soul adjusts to the Afterlife and help them settle in.

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  To Become a Grim Reaper

You need permission from King Enma. Once you become a Grim Reaper, reincarnation is impossible.

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  The Afterlife

It is no different from the human world. The only difference is that the residents are all dead souls. You don't have to eat, but you can. There are supermarkets, parks, and other amenities. It's a good place to live.

Souls are all rational beings capable of conversation.

Since Specters roam at night, it is best not to go out after dark.

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  Butterflies

They are white butterflies. More accurately, they are energy in the form of butterflies made of light. Dozens of them follow a Grim Reaper. Usually around ten, but depending on the Reaper's ability, they can multiply into dozens or hundreds.

They choose the Grim Reaper's partner, their companion. If a Reaper's butterfly attaches to another soul, it means that soul is the Reaper's destiny.