It's a little disappointing that disease as a plot device hasn't caught on with other artists. There should be a lot more than mold that and kill them considering they are bouncing pastries in a forest.
I've always wanted to see something about intestinal parasites, considering some eat trash. I could imagine flukes swimming around or a massive tapeworm.
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.
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.
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.
We're not far apart. In fact, if you think on what passes for canon about poo-poo supposedly not smelling, it's reasonable to believe it would stink. And uneasiness? It's a spike in fungal or bacterial activity..so, literally a case of food poisoning.
edit: yeast is fungus. mushrooms are fungus. mold is fungus. doesn't make sense for yus to contain yeast or eat mushrooms unless they almost instantly crap it out or else suffer attack from within. Still think bacteria infestation makes the most sense.
So the most commonly established canon (subject to artist/writer interpretation) is that the yukkuris, while being animated manjuus, are also "alive" and are treated as an organic living being. In the universe they reside there could be parasites or bacteria that have evolved to take advantage of such creatures. Being a rich source of carbohydrates and protein, a lot of animals turn to eating yukkuris as opposed to the harder to hunt prey animals.
poo-poo is "old" paste that gets expelled periodically from the yukkuri as part of their filling churning and is only really considered "stale". (think old crusty beanpaste) Of course, like everything, it could potentially have bacteria in it, but canonically I don't think yeast was part of the thought process. Yukkuris have also been likened to the Orks in the Warhammer universe, where the things they "believe" come true, to a certain degree. (hence the poo-poo only smells and is toxic to them). Similarly with the concept of "uneasiness". Uneasiness can be caused by stress, bacteria/fungal activity or any number of things and is more commonly tied to yukkuri psychological well-being, but mostly they are uneasy because they "believe" so. There are a few short stories of Anon convincing yukkuris that they're not actually alive, and they turn into manjuus for anons to sell in the store.
Also as part of the more canon thoughts, anything the yukkuri eats turns into paste magically, disregarding things that are poisonous/toxic. But this bit has a lot of different interpretations, going from yukkuris not realizing they're eating poo-poo and enjoying it to not realizing they ate poisonous mushrooms and dying. (depending on how much the author wants to liken yukkuri to actual creatures)