When a yukkuri's stupidity, overconfidence, superiority complex, and/or limited experience causes them to hold a skewed view of the world that's heavily biased towards themselves. Shitheads (and by that extension deibus and wasa reimus) are naturally delusional creatures though not all delusional yukkuri are shitheads.
A lot of koyukkuris are born delusional but unless they're truly shitheaded these delusions can usually be corrected with good parenting. Conversely a relatively humble or level-headed yukkuri can turn delusional if they're too spoiled which is a particularly common mistake among inexperienced pet owners.
These skewed views vary but the some of the most common examples include:
- believing that they're someone special, the chosen one, a hero/king (marisa) or a princess (reimu)
- believing that they're the strongest creature in the world, can easily defeat anyone else, and anyone who manages to fight back must be cheating somehow
- believing that every other creature (especially humans) exist to serve them as their slaves, making them easy is their responsibility
- believing that they cannot make any mistakes at all and if something in their plans went wrong it's someone else's fault
- believing that their (or their children's) cuteness means that they'll be forgiven from any wrongdoings that they do
- believing that everything that a human have (house, food, clothes, etc) are found/given instead of being earned/bought and thus they must have equal rights to obtain those items too, usually claiming "easiness are meant to be shared!"
- believing that saying "don't notice [insert yukkuri type here]" while "sneaking" in broad light and in the open makes them invisible.
- believing puffing up is actually scary or even hurtful against humans and animals.