  [Review for "Chinese Science Bulletin" and CEPC+SPPC Proposal] Rare decays in
flavor physics often suffer from Helicity suppress and Loop suppress. Helicity
flip is a direct consequence of chiral $U(3)$ symmetry breaking and electroweak
symmetry breaking. The identical feature is also shared by the mass generation
of SM fermions. In this review, we use MSSM as an example to illustrate an
explicit connection between bottom Yukawa coupling and rare decay process of
$b\to s\gamma$. We take a symmetry approach to study the common symmetry
breaking in supersymmetric correction to bottom quark mass generation and $b\to
s\gamma$. We show that Large Peccei-Quinn symmetry breaking effect and
$R$-symmetry breaking effect required by $b\to s\gamma$ inevitably lead to
significant reduction of bottom Yukawa ${y}_{b}$. To compromise the reduction
in $b\bar{b}$, a new decay is also needed to keep the Higgs total width as the
SM value.
