  We investigate the sensitivities of the liquid scintillator counter (LSC) at
Yemilab and JUNO to solar neutrino oscillation parameters, focusing on
$\theta_{12}$ and $\Delta m^2_{21}$. We compare the potential of JUNO with LSC
at Yemilab utilizing both reactor and solar data in determining those
parameters. We find that the solar neutrino data of LSC at Yemilab is highly
sensitive to $\theta_{12}$ enabling its determination with exceptional
precision. Our study also reveals that if $\Delta m^2_{21}$ is larger, with a
value close to the best fit value of KamLAND, JUNO reactor data will have about
two times better precision than the reactor LSC at Yemilab. On the other hand,
if $\Delta m^2_{21}$ is smaller and closer to the best fit value of solar
neutrino experiments, the precision of the reactor LSC at Yemilab will be
better than JUNO.
