  We interpret the potential observation of the 750 GeV di-photon resonance at
the LHC in models, in which an $SU(2)$ isospin-singlet scalar boson mixes with
the Standard Model (SM) Higgs boson through an angle $\alpha$. Allowing the
singlet scalar boson to have renormalizable couplings to vector-like leptons
and quarks and introducing sizable decay width of the 750 GeV di-photon
resonance into non-SM particles such as dark matters, we can explain the large
production cross section $\sigma(H_2) \times B(H_2 \to \gamma\gamma)$ as well
as the apparent large total width of the boson without conflicts from the
results obtained by previous global fits to the SM Higgs boson data.
