Suddenly every inhabitant of Gensokyo has a Yukkuri shaped after them resting in their heads 24/7, for what reason? we don't know. . .but that's gensokyo, things like "reasons" and "common sense" are something they don't need.
I heard you like Touhou, so I put your favorite character's head on top of your favorite character. So you can take it easy with Touhou while you enjoy Touhou easy.