The Yurethra is the yukkuri urethra. It acts as an orifice to excrete sugar water, a byproduct of their ability to turn (barely) edible food and sweets into new filling for themselves and use water to hydrate themselves. To avoid accumulating too much water, yukkuris naturally expel water mixed with excess sugar, the pee pee.
Differently to other animals, due to the weird nature of their ermaphroditical existance, with Peni Peni and Mamu Mamu being a unique orifice entirely devoted to reproduction, the yurethra is a different orifice, located between the PeniMamu and the chin. It's not hard to miss, especially with koyukkuris that, lacking bowel control, soil themselves constantly to express extreme happiness or extreme fear.
Due to the constant trickling of sugary water, orphan or neglected koyukkuris in the wild are often prone to dangerous mold, a condition untreatable in the wild. Thus, parent yukkuris care the most about their offspring hygiene.