  Two Higgs doublets respect a mirror symmetry with spontaneous violation so
that their vacuum expectation values can realize a small difference. Under this
symmetry, three newly introduced right-handed neutrinos rather than the
standard model fermions perform an odd transformation. Accordingly the neutrino
masses and the charged fermion masses respectively are proportional to the
difference and sum of the vacuum expectation values of two Higgs doublets. From
a phenomenological perspective, such nearly degenerate Higgs doublets with
large cancellation are equivalent to a Dirac seesaw mechanism with high
suppression.
