  Recently a weak X-ray emission around E ~ 3.5 keV was detected in the
Andromeda galaxy and various galaxy clusters including the Perseus galaxy
cluster but its source has been unidentified. Axino, the superpartner of axion,
with a mass 2E is suggested as a possible origin of the line with R-parity
violating decay into photon and neutrino. Moreover, most of parameter space is
consistent with recent observation by the BICEP2 experiment.
