  We present a detailed chemical abundance and kinematic analysis of six
extremely metal-poor ($-4.2 \leq$ [Fe/H] $\leq-$2.9) halo stars with very low
neutron-capture abundances ([Sr/H] and [Ba/H]) based on high-resolution
Magellan/MIKE spectra. Three of our stars have [Sr/Ba] and [Sr/H] ratios that
resemble those of metal-poor stars in ultra-faint dwarf galaxies (UFDs). Since
early UFDs may be the building blocks of the Milky Way, extremely metal-poor
halo stars with low, UFD-like Sr and Ba abundances may thus be ancient stars
from the earliest small galactic systems that were accreted by the proto-Milky
Way. We label these objects as Small Accreted Stellar System (SASS) stars, and
we find an additional 61 similar ones in the literature. A kinematic analysis
of our sample and literature stars reveals them to be fast-moving halo objects,
all with retrograde motion, indicating an accretion origin. Because SASS stars
are much brighter than typical UFD stars, identifying them offers promising
ways towards detailed studies of early star formation environments. From the
chemical abundances of SASS stars, it appears that the earliest accreted
systems were likely enriched by a few supernovae whose light element yields
varied from system to system. Neutron-capture elements were sparsely produced
and/or diluted, with $r$-process nucleosynthesis playing a role. These insights
offer a glimpse into the early formation of the Galaxy. Using neutron-capture
elements as a distinguishing criterion for early formation, we have access to a
unique metal-poor population that consists of the oldest stars in the universe.
