  A recent Little-Parks experiment on Kagome-structured superconductor
CsV_3Sb_5 demonstrated remarkable resistance oscillations with period
\phi0/3=hc/6e. Here, we perform analysis based on a theory involving three 2e
superconductivity (SC) order parameters associated with the three reciprocal
lattice vectors which connect M points of the hexagonal Brillouin zone. In a
ring geometry we unveil that, as a series of metastable states, phase of one SC
order parameter winds 2\pi more or less than the other two ones around the
ring, which yields local free energy minima at integer multiples of \phi0/3.
Intriguingly, the ground-state degeneracy associated with a Z_2 chirality is
crucial, and the Higgs-Leggett mechanism stabilizes domain walls (DW) between
chiral domains. At low temperatures DW are expelled from the system resulting
in free energy minima only at integer multiples of \phi_0. Our theory explains
successfully the 6e SC observed in experiments, which opens a door for
approaching rich physics of Kagome superconductors.
