A page in the yukkuri owner manual mentioned: When yukkuri starts asking for little ones, consider it like it's their end of life.
Stopping yukkuri's desire to breed is harder than telling a heavy smoker to stop. Mister had his own comparison, it's more difficult than telling high school boy to not masturbate.
Mister had a Reimu he had raised to softball size and playing with ball in the room. As suggested by the manual, Mister kept a relationship like house owner and resident with Reimu.
He do understand that strong drive to breed in yukkuri. They're weak and need to breed a lot to survive. For example, fish could lay millions of eggs, but only a few of that batch actually made it to adulthood. Same with yukkuri, they made a lot so some lucky ones would made it to adulthood.
Yukkuri's desire to breed starts when they grow to juvenile stage. Among wild and strays, this is the age yukkuri became independent from their parents. They will find their own couple and find their own easy place. From generations of experience, other than the stupid individuals, yukkuri avoided the winter or rainy seasons to breed. They also avoided dry summers so the time they made children are limited.
Not so for pet yukkuri. Holding back is no matter of life or death like their counterparts outside, so they're in breeding mode all year long.
Mister compared pet yukkuri to a rich boy living spoiled in a luxurious house. He can get everything he wanted, any food he wanted. The rule is only one: no sex. That includes no porn, no masturbating, no having sexual relationship with girls.
One or two days might be possible, but forever is impossible.
As soon as that boy get out of the house, poor girls starting to approach him with various appeals. Those who do it slowly to those who straightforwardly ask him for sex. Even a gold badge yukkuri would break.
That's why it's suggested to just kill the yukkuri when they start asking for little ones. If you commited to them, they will grow without any upper bounds. Yu-Junk factory mass produced yukkuri for human's enjoyment and they can be disposed anytime the owner had enough. Just give the yukkuri ramune candy and kill them when they're sleeping.
Reimu who finally grown to a basketball sized juvenile finally want to marry.
Seems like she wanted to marry a stray Marisa from the natural park nearby.
I bought baloon from the 100 Yen shop, blow it, and put it into Reimu's Place.
“Reimu, if you live with your couple, your place will become smaller. Concretely, like this.”
“This is still fine.”
“You’ll make little ones after marrying, right ? When the little ones grow big, the place will become even smaller.”
I blow the balloons bigger and put it in Reimu’s place.
“thi, this is tight. But we can always do rub rub happyness~!”
“When little ones grow big, then say they want to marry and have little ones, what will you do ? It will become more cramped.”
“…yu, that’s right! Mister could expand Reimu’s place! Reimu will pay!”
“Then my place will become smaller and I can’t feel easy, so I wont do it no matter how much you’re paying.”
“Yuu… but! Reimu want to take it easy with Marisa!”
“Reimu, between me and you, who’s smarter ?”
“Mister. Mister taught a lot of things to Reimu. But Reimu is still better in singing!”
“Right. So the smarter Mister will teach you this. You’ll live longer if you don’t marry or have little ones.”
“What is Mister saying? Yukkuri exist to take it easy! Little ones are really easy!”
"You mean, Yu-life is meaningless without little ones ?”
“No! It’s really easy if there’s little ones. If we’re easy, we can also live long!”
Those who are easy are great, strong and wonderful.
That’s why if you’re easy, everything will be fine. And little ones are very easy. Well, that’s yukkuri’s logic.
“I’ll ask you again one more time. Believe in what smart Mister is saying, would you give up marrying and having little ones ?”
“No! Mister is smart, but just this one time Mister is wrong!”
“…I see. Okay, I wont say anything more. As long as you pay for your rent, I’m fine with it. After all, that’s Reimu’s place so just do as you want.”
After divorcing scums who are clearly targetting Reimu, Mister let Reimu marry a nice-looking stray Alice, the fourth candidate. He had warned Alice to have mammalian pregnancy, but Reimu forced a stalk pregnancy and had two pairs of babies.
Food is not that difficult because yukkuri food are cheap and it can also be exchanged by bringing yukkuri poop to the store to be processed.
But when the babies grow to adult, their place became cramped. The children often pay with food to enter Mister's space too.
He thought, why didn't he castrate his yukkuri before ? Of course it needs a long talk with the yukkuri because most yukkuri will fall to depression when knowing they can't have children anymore. They fall to something nobody would want to have as pet anymore.
Reimu finally suggested they will become strays, that way they wont cause trouble to Mister anymore.
Mister showed video of stray's life to the family, but Alice used to be a stray, so she can teach her family how to survive.
Mister's last warning is to not go to the park (where the children had their future couple. Mister told them there's routine extermination there so likely those yukkuri are dead and they will be too if they go there.
Actually it's a lie. Mister still have troubles in disposing them because it's against the law to throw away living yukkuri. The only peoples who will accept yukkuri in who wanted children are either Factory or Abyuser.
Finally after failing to find someone who will take the family, he made a talk with owner of a cove who will accept the yukkuri in his ground. He's not making any promise though. Mister can throw his yukkuri there, but there will be exterminations and even peoples coming to hunt for yukkuri.
When they parted, Mister do rub rub with his yukkuri for the last time. Usually it's just to his hand, but this time he did rub rub with his cheek to all the yukkuri before returning to his home.
There, he felt lonely. The six yukkuri living in his home is no more.
It's true what's written in the book. Consider the yukkuri is reaching their end of life when the yukkuri starts to desire children.
Yukkuri are cute for pet only when they're still children.
Well, the best way to heal the loss of a pet owner is getting another pet. This time, Mister want to try a silver or gold badge, and preferably castrated yukkuri. Even without children, that yukkuri can still have a happy life with her couple.
When coming home from yukkuri shop after work, Mister is very excited to have a new yukkuri pet. He didn't notice a car he passed by where many yukkuri are locked in transparent box. Among the 10, 6 yukkuri reacted when seeing him. They're crying and screaming, but their voice never reached the excited man outside the box.