When a yukkuri's tastebuds are spoiled from eating high-quality food (high-grade yukkuri food, sweet sweets {including other yukkuris}, etc), and then said yukkkuri consider anything of lower-quality (wild grass, insects, cheapo yukkuri food, leftovers, etc) inedible. This causes them to refuse to eat or vomit when attempting to eat low quality food, throwing tantrums demanding to be fed sweets instead. Eventually most yukkuri with spoiled tastebuds will starve to death.
Mainly happens to koyukkuris due to their inexperience and inability to surpress their desires. Adult yukkuris are usually smart enough to avoid sweets though shithead or dumbass adults can be affected too.
Wild yukkuri or gutter trash parents often go out of their way to prevent their children from eating sweets to prevent this and will in fact often panic if they notice their child seeing a sweet food. Conversely some humans intentionally feed stray yukkuri sweets as a form of abuse knowing they will die from starvation.
Most pet yukkuris technically suffer from this but as they have easy access to high-quality food it usually doesn't matter for them unless they get abandoned.
