  We report a fuel-dependent reactor electron antineutrino ($\overline{\nu}_e$)
yield using six 2.8 GW$_{\text{th}}$ reactors in the Hanbit nuclear power plant
complex, Yonggwang, Korea. The analysis uses $850\,666$ $\overline{\nu}_e$
candidate events with a background fraction of 2.0 % acquired through inverse
beta decay (IBD) interactions in the near detector for 1807.9 live days from
August 2011 to February 2018. Based on multiple fuel cycles, we observe a fuel
$^{235}$U dependent variation of measured IBD yields with a slope of $(1.51 \pm
0.23) \times 10^{-43} $cm$^2$/fission and measure a total average IBD yield of
$(5.84 \pm 0.13) \times 10^{-43} $cm$^2$/fission. The hypothesis of no
fuel-dependent IBD yield is ruled out at 6.6 $\sigma$. The observed IBD yield
variation over $^{235}$U isotope fraction does not show significant deviation
from the Huber-Mueller (HM) prediction at 1.3 $\sigma$. The measured
fuel-dependent variation determines IBD yields of $(6.15 \pm 0.19) \times
10^{-43} $cm$^2$/fission and $(4.18\pm 0.26) \times 10^{-43} $cm$^2$/fission
for two dominant fuel isotopes $^{235}$U and $^{239}$Pu, respectively. The
measured IBD yield per $^{235}$U fission shows the largest deficit relative to
the HM prediction. Reevaluation of the $^{235}$U IBD yield per fission may
mostly solve the Reactor Antineutrino Anomaly (RAA) while $^{239}$Pu is not
completely ruled out as a possible contributor of the anomaly. We also report a
2.9 $\sigma$ correlation between the fractional change of the 5 MeV excess and
the reactor fuel isotope fraction of $^{235}$U.
