In the forest, a very starved Marisa is crawling to hunt for food. From her dried and cracking lips, she weakly beg for food to came out.
For the last few days, the only thing filling her crooked hat are just grass, bitter grass. Marisa and her wife Reimu might still be able to barely sustain themselves with grass, but for the inefficient baby yukkuri, bitter grass can't be called edible thing. They want easy foods and bitter grass wouldn't convert to paste.
Yes, Marisa has a little one waiting for her at home, her last hope.
Her wife Reimu understands, those grasses are the only thing they can find. That's why Reimu doesn't blame Marisa, she just talked to herself why there's only this and the little one would die.
The place Marisa lives in is not a barren mountain. There's a lot of trees and of course insects. Unfortunately, yukkuri are weak and stupid. Marisa are not even observant enough to find a green caterpilar on green grass. She chased futilely on a butterfly that can fly and move a lot faster.
Fruits here are taken by other animals a long time before yukkuri can find them. The only insects they can get are from the corpses.
Marisa's house is a dent between roots of a tree. There's a branch above that protects them from rain, but do not much to protect them from cold wind. Yukkuri can't make anything. The only tool they have are their sugar teeths that can not do much to help them dig a place to call home. A hole that can fit several heads is already something to call a luxury.
Marisa's last child, a smaller than normal baby Reimu, is crying. She can only curse her life, but no voice came out. Even after Reimu and Marisa tried chewing the grasses soft, little Reimu vomitted it out. Her body doesn't have the capacity to change it into paste anymore.
Reimu wished to return to the time she hasn't been born yet. That time is very easy, she's feeded with endless dream of easy life. Eating sweets sweets and sleeping, nothing but happyness. Never she realized the world will offer none of it.
Orange Juice would heal her, but that's not something yukkuri can make. Her body has already survived by allocating all energy left in her paste to sustain her paste core, but even that has finally reached its limit.
Reimu and Marisa can only sobs. Ever since their ancestors, they already know to not make loud noise or animals would find and kill them.
They can make another little one, but they will just die the same way. Winter is coming, and surely both yukkuri will froze to death in starvation.
Decades ago, yukkuri are accepted by human, until they showed their true nature. Then a nationwide yukkuri hunt is done, killing tens of thousands of yukkuri every day. Their number dwindled down.
Survivors escaped to the wild, where they're challenged by the local animals.
The only better time is after winter. When spring arrived, only a fraction of yukkuri survived so competition is low. There's also better food to be found, such as occasional insect corpse to eat. Thanks to that, yukkuri followed their instinct to mate.
Reimu is living is a better house after marrying Marisa. She barely survived winter by eating her parents and there's not been any good thing happened in her whole life. The little ones hanging from the stalk growing on her head is the only easy thing she has.
Five yukkuri fruits, shaking when Reimu greeted them. The response bring happyness to Reimu, making her forget the suffering she had lived through.
Then there's a buzzing voice. Reimu thought it's the fly going to her poo poo. But because of the smell, Reimu always bring out her poo poo outside.
In fact it's not. A hornet landed on Reimu's stalk, bringing terror to her paste. When Marisa came home, she too can only freeze in fear, giving empty threat while clearly in terror.
Then the hornet fly away. Both yukkuri's easy life continues, until a week later when the babies are finally ripe.
Two pairs of baby Reimyu and Maricha are born, and they happily greeted their mother. Reimu is in heaven.
But the last Maricha on the stalk turns black. Then from inside, bees breaks through the thin dough skin and crawl out. Their wings are not dry yet, so they crawl outside to the light.
Reimu can't react. Her children screamed in terror from seeing their own little sister killed gruesomely by the bees. Then they're also panicked when ants came in.
Before they learned about the world, a trauma has been implanted into yukkuri to fear insects, especially black insects.
Researchers are baffled. It took just several decades for parasite species targetting yukkuri to show up. Usually it would take hundreds or thousands of years. There's much theory, but nobody are sure.
The hornet laid their eggs on stalk, and usually the egg flows to the last baby. There, the larva will eat the baby yukkuri from inside, starting from the tongue to make it unable to talk.
The pain resulted made more paste delivered, giving more nutrition to the hornets. The paste flow also give the illusion that the baby is growing bigger.
It's when they finally damaged the paste core when breaking out that the baby is released from its suffering.
Another time, a Maricha is running in the middle of the night. A little thin, but she's from a comparably gifted family to grow this big.
She run to look for water to drink. Although she think it's strange because she had just drank, the thirst is too much to bear.
Maricha is not spoiled. Her parents love her, but also strict on her. She also learned better to not go outside by seeing the less obedient siblings of her die one by one.
So, it's this strange thirst that forced her out, to the water, overcoming the ingrained fear of water that yukkuri has.
She jumped and keep on drinking so much, her paste change into something like thick soup. Finally, her body can stand no more and ruptured, letting the pressurized paste inside escape together with white string like creatures.
These are parasites living in the water. They grow inside yukkuri's paste and when mature, absorb water from the yukkuri to make them feeling thirsty, thus sending the parasites back to water for mating and hunting their next victim.
Not just those two. Insects, animals, even fungi evolved to become yukkuri parasite. A whole ecosystem focused on yukkuri as the lowest rank is formed.
Eventually, the lack of yukkuri made the parasites specialized. For example, they only target specific kind of yukkuri instead of all variations.
As the yukkuri population falls, so does the parasites, allowing the yukkuri to repopulate themselves. With this natural balance at work, yukkuri wont go extinct, which in extension ensure the survival of the parasites.