That butterfly was one of the "death butterflies" that Yuyuko-sama takes close care of.
Two days ago...
Reports came in that the Misty Lake located at the root of Youkai Mountain was swarming with death butterflies.
This morning...
We arrived to find the Misty Lake surrounded by comatose animals and youkai who had come in contact with the butterflies.
Three days ago.
Death butterflies have the power to show dreams of a paradise known as Kasho. It is said that once the weak get to play in the land of Kasho, they never open their eyes again.