  It is pointed out that a natural introduction of quintessence is an axion
with an almost massless quark. With an appropriate gauge or discrete symmetry,
one can obtain the quintessence potential height of order $(0.003 eV)^4$. Even
though the QCD axion with almost massless up quark is a possibility, we stress
the almost massless quark in the hidden sector together with the QCD axion
toward the quintessence.
