House yukkuri (often simply called house yu) is a special kind of yukkuri. They're effectively the yukkuri world equivalent of cockroaches: small in size (about 1/3 of a normal yukkuri), lives secretly inside human homes (their namesake), and reproduces by laying eggs usually in greater quantity than normal yu reproduction. It is said that the taste of their eggs is similar to chocolate beans. House yu's live off entirely off of human foodstock and garbage.
Unlike normal yukkuri's, a house yu generally don't have the big aspirations of normal yukkuris (such as becoming a pet or a hero) and tend to focus almost entirely on food and survival. House yu's often are wise enough to know they don't stand a chance fighting against humans. However they tend to have a one track mind once they're hunting for food and will often not notice the presence of a human until they're actively being attacked.
While a house yu's fears humans, they tend to not fear a non-hunter pet yukkuri. In fact house yu's can be dangerous to pet yukkuris, especially Koyus. House yu's are generally not smart enough to realize that harming a pet yukkuri can attract the attention of their owners. There are known cases of more timid pet yukkuris either being threatened to give up their food or straight up being killed by house yu's. Conversely a human who owns a hunter-yukkuri as a pet such as Momiji, Chen or Remilia might also teach them to hunt and kill house yus.
Often when an infestation is bad enough a human can call a pest control service to get rid of them. These pest control often rely on a trained predatory yukkuri (usually a Momiji) or poison gases.
House yu's are often considered distinctly different from normal yukkuris and humans in the yukkuri world seems to view them as completely different species than a regular yukkuri. A person who is fine with a normal yukkuri might be scared or disgusted by a house yu (as they view them as cockroaches). They're often killed with a poison spray or swatted with an object (like a cockroach) as humans tend to be disgusted to hitting them directly with their bare limbs. They are also almost universally considered pests, even yukkuri-lovers and yukkuri-lover communities tend to not have a problem with the killing of house yu's.
Called ieyu (lit. home/house yu) in Japanese.