  An annual modulation signal due to the Earth orbiting around the Sun would be
one of the strongest indications of the direct detection of dark matter. In
2016, we reported a search for dark matter by looking for this annual
modulation with our single-phase liquid xenon XMASS-I detector. That analysis
resulted in a slightly negative modulation amplitude at low energy. In this
work, we included more than one year of additional data, which more than
doubles the exposure to 800 live days with the same 832 kg target mass. When we
assume weakly interacting massive particle (WIMP) dark matter elastically
scattering on the xenon target, the exclusion upper limit for the WIMP-nucleon
cross section was improved by a factor of 2 to 1.9$\times$10$^{-41}$cm$^2$ at 8
GeV/c$^2$ at 90\% confidence level with our newly implemented data selection
through a likelihood method. For the model-independent case, without assuming
any specific dark matter model, we obtained more consistency with the null
hypothesis than before with a $p$-value of 0.11 in the 1$-$20 keV energy
region. This search probed this region with an exposure that was larger than
that of DAMA/LIBRA. We also did not find any significant amplitude in the data
for periodicity with periods between 50 and 600 days in the energy region
between 1 to 6 keV.
