Fuki (腐酒, Fuki?, lit. Rotten alcohol) is Kouki that has turned rotten instead of becoming a mushi. While Kouki appears as a golden sake, Fuki is a reddish muddy paste that wells up from underground springs. It smells like a sweet fruit liqueur, but it is toxic. If a person drinks it in its basic form, they are likely to die. However, in rare cases, a person may withstand the poison and the Fuki will mix with their blood and seek out life without any conscious thought, with the person unaware that the Fuki is now part of them. In turn, the Fuki grants its host with some unusual powers.
Symptoms[]
Fuki is passed down through bloodlines, from generation to generation. Only a rare few are able to use its power, however, and those who can't are slowly poisoned and don't live very long. In its early stages, the poison causes the person to experience short periods of pain that presumably get worse in intensity. If left untreated, they will end up coughing up blood and dying.
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The eye-shaped birthmark of the Fuki on Tatsu's palm.
To those who can use its power, the Fuki appears as a birthmark on the palm in the shape of an eye. It gives off a sweet scent that puts prey in a trance-like state, making it useful for hunting, though the animals killed will smell rotten no matter how fresh they are. The person infected with the Fuki rapidly becomes drunk off of its power, as the Fuki is insatiable in its search for living things. Eventually, the host will start to kill things needlessly. If the host isn't treated, the Fuki will start to take control. The host's body will become more transparent and no longer have a shadow, until eventually the Fuki takes over entirely and the host loses their body and soul, fully becoming part of the mushi world.
Weakness[]
Giving a certain amount of Kouki to its host will make the Fuki within them dissolve.