Have you ever meet a white volleyball-like object on the ground ? When you kick it, it doesn't fly far and leave a disgusting feel on your feet. That's the puffball.
They have no use and grow suddenly in random place without anyone noticing.
To see the mistery of their growth, we will observe a creature that looks like puffballs, the yukkuri.
First is a baby Marisa. She seems to be talking to someone, but she's alone. The baby also ate dry leaves happily. Normally dry leaves are not easy at all, let alone happyness-tasted. But this Marisa surely is happy.
Fast forward and she has grown to a Koyukkuri. Again, she ate the dry leaves happily and in addition also eat her own shit. This is against yukkuri's common instinct.
Fast forward again, the adult Marisa is clearly losing more and more of her capability. Even as her hat is lost, she doesn't care because she's in total bliss, eating away dry leaves mixed with her own shit.
Then Marisa moved, starts humping to the air and sprayed out powder from her peni peni.
Compared to the normal yukkuri, shown from Factory's documentation, the ejaculation is clearly different. The wild Marisa's ejaculation contains spore.
Then finally Marisa stopped moving. Her hair are lost as well as her facial feature.
When split open, there's no more paste left, only homogenous white matter.
The discovery leads to the usage of spore as an effective tool to clean away the useless yukkuri.