Well, he probably think his idea is good. Make Reimu suffer in place of his ex, and then move on when Reimu finally die.
Psychologists are finding out now that acting on your violent behaviors in order to 'cope' is actually very unhealthy as it leads you to always cope with your pain by inflicting pain on something (or someone) else.
He's either taking care of them (possibly a kennel?) or perhaps he's a breeder/raiser/trainer, and now Reimu has been selected for adoption. so he'd give her one more day with them together.
But no one had to die. Instead, it's a bitter-sweet ending. Everyone got what they really wanted. Even though Marisa can't go back to being Marisa, she is with her child, the one she worked hard to see again. It may not be perfect, but it's close-a-freggin'-nuff.
I think it comes down to how much deus ex machina magic one allows yukkuri. Why would something enchanted even need to eat, as its' life force is outside scientific principles.
That said, the biggest reason I think yus have parasites (even if benign) is one of their most notorious actions-farting. Why do yus fart if not for the presence of bacteria? Even so, their constant shitting might be what keeps (say) tapeworm larvae from the life cycle and keeps the sweet paste ones from all turning into vodka jello shots.
Fart = yeast.
Stool = I would say that the reason they have the function of stool is because they have to process food. The food that processes and becomes the replacement paste pushes out the bad paste. Obviously, when they poop, there must be some kind of bacteria in it; possibly yeast is what they smell, or the bacteria that was used to ferment their paste.
Anyway, they're completely magical golems, so we can make it up as we go along. I'd still like to flesh it out as much as possible.
Theoretically, anything is possible, however, it's hard to discern what -could- affect a yukkuri, other than mold. Their body is bread, their innards are any type of filling. While most fungi just want moisture to begin their growth, certain parasites require more than that, and the level of sugar of yukkuri would probably act as a repellent against most common parasites. Probably wouldn't know what to do.
Besides that, magical paste core that turns anything that churns in it into paste. I never understood how mold was more than a surface issue for them, but as soon as the roots reach into the paste, it should just get digested. :x
That aside, I would assume, since yukkuri are not something that is 'supposed to exist,' and is theoretical, ideally, they wouldn't be vulnerable to parasites because a parasite wouldn't recognize the host as something that is capable of being a host.
Yeesh. Takumi can really bring a tear to one's eye with his work.
And I'm sure AngelofDeath will be here shortly for a creatively pithy reply featuring whatever made-up characters he chooses to use today.
Srsly. Was there any point to dragging this out any further? Why not have the remains explode into firey ash that lands in a yukkuri clan and burns the whole place down around them?
Would kinda like to see yus make clothes out of scrounged stuff. I think the only other time I saw this was the story Hitosura posted about a platinum Reimu that made what looked like a raincoat and hat to cover where she'd been maimed.
Maybe ordinary yus don't have the self-awareness to either see themselves naked, but I'd think they'd see clothes as easy as accessories. Myself, I don't think bodied yus are born with clothes and would instinctively try to make or get some because they're that much more humanoid.
That raincoat/hat was actually sewn out of a Marisa hat that she took off of some shithead strays that tried to kill her. It comes later in the story.
This whole idea of indiscriminate mass extermination isn't my cup of tea, not when it consists of an entire clan of mostly niceheads being wiped out. It only encourages the shithead population to proliferate.
That. If they're not disturbing anyone nor being a pest to nearby residents, then a mass extermination shouldn't be necessary.