Lets do hybernation!
This is a yukkuri clan. Inside it is a couple of Marisa and Reimu.
Both has just finished preparing for winter and gathered enough food for both. Winter is a difficult season, but they had planning.
Reimu is a sole survivor of her family in the previous winter. She's taught a lot of thing by the chief and is quite smart. At the very least, she doesn't hinder others so she had good image among the yukkuri clan members.
Marisa is a typical Marisa. Strong, proud, hate to study. But she know her position and what she must do. Her hunting skill is also in the better part of the clan members.
And thus, they started their winter. Before going to sleep, Reimu and Marisa greeted each others and the three babies hanging on stalk growing from Reimu's head.
Yukkuri's hibernation means lowering their activity and carefully eat the stockpile of food gathered in preparation. They only doze lazily in their nest to save energy, then wake up to eat. Not exactly so different from the usual.
They avoid activities that take a lot of energy, such as child birthing. This is where Reimu's plan went wrong.
55 days later, Reimu's family experienced the terror of winter. Reimu has gave birth to her babies. The two elder Marisa can be seen as smart yukkuri that are born one in ten years. They quickly understand and hold their hunger together with their parents. Problem is the last daughter Reimu who's useless and selfish. The only good (or regretted) part of Reimu is she's born into a kind family that spoiled her.
Each meal, the parents only eat a little. Both KoMarisa shared their food to their crying little sister. Even so, that Reimu is not thankful at all. She still tell her father to go out and hunt in the cold winter, calling her family useless. A really crush-worthy yukkuri.
66 days... spring is coming closer, but how long can they survive ? Father Marisa aplit herself for her family to eat. But after that long and painful winter, there's almost no paste left.
Both KoMarisa is saddened from seeing their father. In the other hand, KoReimu is happy because there's more food. Her sisters already feel nothing for that KoReimu.
Reimu still don't think it will be enough. While contemplating, she remembered her childhood and how her parents sacrificed themselves so she can survive. This memories has long been repressen in her mind, but now she think she can understand what her mother feels.
When spring came, KoReimu jumped out of her nest arrogantly to the world. She's the only survivor.
Without their parents, there's nobody to stop them, especially that need-to-be-crushed KoReimu. She then killed both her malnourished sisters and survive. Even so, she still think all of them should be doing happy pee pee because they have made her survive.
There's a lot of things to be regretted. If just this KoReimu had 1/10 of her sisters' good side. If just Marisa and Reimu would not spoil this child or just throw her away.
If they do, all these tragedy won't need to happen. The clan would get two young yukkuri who could become the next clan leader instead of this Reimu.
"It's like flying in the sky!"
Reimu is happy to see the view from the sky. But her new slave is not listening. The young Remirya is just so happy to succeed in her first hunt and can't wait for her parents' praise.
This Reimu will fall into a living hell soon.
Koyukkuri who survived the winter alone faced this same risk. They don't have any survival skill and they have nobody to protect them. There are those who managed to hide or got protected by other yukkuri family in time, but Reimu is not so lucky.
Most of the yukkuri who survived winter is actually not the best yukkuri.
The better yukkuri planned their winter carefully and spend their effort to gather food for their family. The result is like what can be seen with this family.
In contrary, most of the survivor is actually the second-rate yukkuri. They failed to prepare food and their hurriedly built barrier is not tight enough to block the winter cold. They shiver in the cold and fall asleep, then their paste frozen up, causing their body to shut down completely until they're defrosted in the spring.
This is one of the reason why yukkuri will never evolve into something better. Once every year, they're weeded out until nothing is left but useless yukkuri.
There's a reason why yukkuri keep on doing this. It's the survivors. It's the Patchouli family. Her husband is Marisa, so she doesn't have trouble with food. Moreover, Patchouli is too weak so she can't gave birth to many children. And thus, they managed to survive the winter.
The frozen manju in the other hand, can't explain in detail why they survived and nobody would believe them anyway.
This is the dynamic of yukkuri population. In spring, they breeded and refilled the numbers that died in winter. Summer wiped out scores again. In autumn, they breeded again. And finally in winter, with that useless method, the good yukkuri are eliminated again.
What about a clan with Dosu ?
In Remirya's nest, mother Remirya is teaching her daughter how to suck paste. Reimu is suffering so her paste is really sweet.
So she wont die easily, mother Remirya forced Reimu with bitter grass, making her suffer more.
Young Remirya is so happy to be praised. She wanted to share, but her mother said she will find her own meal. She also reminded Remirya not to eat too much or she'll turn into a bodied yukkuri and life will get more difficult. If you had enough, just kill her. Remember, don't eat until your stomach is full.
Watching the family, Reimu remembered her family and cry while regretting what she has done.
Reimu can't grow from being malnourished. Although still egging for help, she also lost all hope, even asking to be killed. Until the day young Remirya left the nest, she eat and torture Reimu continuously.
Reimu became the best family dinner in the night of their parting. That time, Reimu left no shade of her former self anymore.