Sometimes also called exploration party, adventuring group, etc
A group of koyukkuris (usually 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, though sometimes the leader barely survives.
Consists of a group of entirely koyukkuris. Any solitary yukkuri adventure isn't tagged this even if she declares herself an expedition squad (such as pool #1951). Any expedition group that includes even 1 adult also shouldn't be tagged this.