  The values of Hubble constant H0 by direct measurements with standard
distance ladder are typically larger than those obtained from the observation
of cosmic microwave background and the galaxy survey with inverse distance
ladder. On the other hand, although the errors are still large, various
determinations of the value of matter density parameter Omega_m are consistent
with each other. Therefore, it is possible that the difference in Hubble
constant is translated to the difference of physical matter energy density
omega_m = Omega_m h^2, where h = H0 / (100 Km/s/Mpc). In this article it is
examined the possibility of an increase of the physical dark matter energy
density (comoving energy density without the effect of expansion of the
universe) by a fast transition at a certain value of redshift as a possible
resolution of the Hubble tension. A phenomenological fluid model of the dark
sector, which is the modification of a so-called unified dark matter model, is
introduced to concretely realize such a fast transition in the physical dark
matter energy density.
