There were many speculation as to their appearance, such as aliens, biological weapons and god messengers.
But the exact cause is unknownA lost decapitated creature was discovered!!Yukkuris, seemingly understanding and speaking simple human language, surprised the entire world when it appeared.October of 2004: A mysterious manju-shaped life form suddenly appeared without warningAppearanceThe world's most famous Yukkuri ReimuSuddenYukkuri...Take it easy!!!