Pee Pee is the yukkuri equivalent of human urine, and a natural byproduct of Yukkuri metabolism. Excreted by the yurethra, or "pee hole". While most biological lifeforms use urine to expel harmful substances from their bodies, yukkuris, who lack a true renal activity, simply expel some sugar diluted with excess water, thus excreting sugar water.
Despite being only sugar water, thus hypothetically collectible for consumption, yukkuri find their own "pee pee" as distasteful and stinky as their poo poo, openly voicing their disappoint and trying to get rid of it by every mean. Especially among koyukkuris, its not infrequent seeing a small ko thrashing around in a puddle of freshly made pee pee, begging its parents or its owner to clean it and even developing anti-yukkuritis, a terminal form of depression, by constant exposure to its own pee. As such, koyukkuris bond easier with the one, parent yukkuri or human, who keeps them clean.
Being pee pee is mostly water, it also holds the same risk of a source, even if little, of clean sugary water. Despite sugar having a somewhat healing effect on yukkuris, high concentrations of water may be fatal; in Shell Marisa a jealous komarisa managed to melt its little, Shell Komarisa sister, by urinating on it while already wounded. Also, shithead koyukkuris and some spoiled adults, may pee on their opponents or even on "Mister Humans" to show their utter disrespect for them.
koyukkuris are often seen peeing as a way to express their feelings; a happy koyukkuri will lose its bowel control, leading to the happy pee, in which the koyukkuri smiles and giggles with a blissful expression while pee trickles out of its yurethra. Despite looking odd, that shouldn't worry a prospective owner, as for a koyukkuri is normal lose its bowel control when overcome by intense emotions, even if positive ones. However, a koyukkuri may also end up soiling itself in fear, mostly when faced with scary situations. That poses some issues with incompetent Anons owning premature yukkuris or pre-verbal kos, as they may forget to pay attention to the body language clues (the happy pee is often accompanied by a blissful smile and narrowed eyes, while a scary pee by eyes wide open and strangled, faint yuu-ing noises) and believe a scared koyukkuri as healthy and happy, or an happy koyukkuri as scared, swiftly removing its source of happiness.
A common illness promoted by pee pee, especially among orphan, stray or neglected koyukkuris, is the dreaded mold. As pee pee is sugar water, a koyukkuri left wallowing on the pee pee it just made, without being able to be cleaned or dried, will always have a damp bottom, promoting the growth of mold. In nature, parent Yukkuri take great attention and care to clean and dry their offspring still unable to move freely every time they pee and often resort to apply small leaves on their anyaru and yurethra as diapers, to ease the cleaning operations. In the city gutters, the lack of hygiene culls a large number of koyukkuris every day, with pee and molds literally melting their tiny bodies.