  Following Shin et al. (2023b), which is a part of the Systematic KMTNet
Planetary Anomaly Search series (i.e., a search for planets in the 2016 KMTNet
prime fields), we conduct a systematic search of the 2016 KMTNet sub-prime
fields using a semi-machine-based algorithm to identify hidden anomalous events
missed by the conventional by-eye search. We find four new planets and seven
planet candidates that were buried in the KMTNet archive. The new planets are
OGLE-2016-BLG-1598Lb, OGLE-2016-BLG-1800Lb, MOA-2016-BLG-526Lb, and
KMT-2016-BLG-2321Lb, which show typical properties of microlensing planets,
i.e., giant planets orbit M dwarf host stars beyond their snow lines. For the
planet candidates, we find planet/binary or 2L1S/1L2S degeneracies, which are
an obstacle to firmly claiming planet detections. By combining the results of
Shin et al. (2023b) and this work, we find a total of nine hidden planets,
which is about half the number of planets discovered by eye in 2016. With this
work, we have met the goal of the systematic search series for 2016, which is
to build a complete microlensing planet sample. We also show that our
systematic searches significantly contribute to completing the planet sample,
especially for planet/host mass ratios smaller than $10^{-3}$, which were
incomplete in previous by-eye searches of the KMTNet archive.
