  Chiral thermodynamics of charmed mesons is formulated at finite temperature
within a $2+1+1$-flavored effective Lagrangian incorporating heavy quark
symmetry. The charmed-meson mean fields act as an extra source which breaks the
chiral symmetry explicitly. This leads to effective interactions between the
light and heavy-light mesons, which intrinsically depend on temperature.
Effective masses of the scalar and pseudoscalar charmed-mesons tend to approach
each other as increasing temperature, so that the splitting between the chiral
partners is reduced. These chiral splittings are shown to be less sensitive to
the light-quark flavors, attributed to the underlying heavy quark symmetry.
Consequently, chiral symmetry restoration is more manifest for the strange
charmed-mesons than for the strange light mesons. The effective masses are also
compared with the results in the one-loop chiral perturbation theory. A
substantial difference is found at a relatively low temperature, $T \sim
f_\pi$.
