Young Vagrants are enemies similar to the Wandering Vagrant. They tend to show up on UES Contact Light and spawn as elites due to this. They have as much health as a small boss and hit as hard a Rock Golem in most cases. Despite being a Wandering Vagrant sub-type, they do not have a top-screen health bar and are not guaranteed to drop items, but will give off large amounts of money and experience.
They should be treated with some caution, but are not the most pressing issue aboard the U.E.S. Contact Light. Many may spawn at once, but continued movement will typically guarantee they never hit the player. Telling whether or not one is an elite it is difficult until they fire Nematocysts.
Their Monster Log unlock the Wandering Vagrant's Monster Log, so their high spawn rate in the U.E.S. Contact Light can be useful to obtain Wandering Vagrant's Monster Log faster.