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A group of koyukkuris (usually a trio of Maricha sisters) adventuring away from their home without adult supervision, typically against their parent's warnings. Almost always leads to the death of all of them, either by accident or by picking a fight with a human.
Sometimes the koyukkuris even admit that their expedition goes against their parent's warnings (the warning is usually "don't go too far from the house/clan since it's dangerous") but their unecessarily high sense of adventure cause them to instead get excited at doing something that is "forbidden". This of couse always backfires as once they get into trouble, they'd be far away from their parents and thus have no hope of being rescued.
"Maricha expedishion squad departsh now nanoje!"
Nobody here but us chickens!