proposal
Two yukkuris promising to get married. As adult yukkuris usually just get hitched right away, proposals are mainly done by koyukkuris who promises eachother to get married once they're older. Often the "future-husband" would give a present to the "future-wife", sort of like an engagement ring.
As is the nature of the yukkuri world however, often the two would never actually get married for one reason or another (usually because one or both died)