  We study the dark nature of GRB 130528A through multi-wavelength observations
and conclude that the main reason for the optical darkness is local extinction
inside of the host galaxy. Automatic observations were performed at
BOOTES-4/MET robotic telescope. We also triggered target of opportunity (ToO)
observation at the OSN, IRAM PdBI and the GTC+OSIRIS. The host galaxy
photometric observations in optical to near-infrared (nIR) wavelengths were
achieved through large ground-based aperture telescopes, such as the 10.4m GTC,
the 4.2m WHT, 6m BTA, and the 2m LT. Based on these observations, spectral
energy distributions (SED) for the host galaxy and afterglow were constructed.
Thanks to mm observations at PdBI, we confirm the presence of a mm source
within the XRT error circle that faded over the course of our observations and
identify the host galaxy. However, we do not find any credible optical source
within early observations with BOOTES-4/MET and 1.5m OSN telescopes.
Spectroscopic observation of this galaxy by GTC showed a single faint emission
line that likely corresponds to [OII] 3727\{AA} at a redshift of 1.250+/-0.001
implying a SFR(M_sun/yr) > 6.18 M_sun/yr without correcting for dust
extinction. The probable extinction was revealed through analysis of the
afterglow SED, resulting in a value of AV >= ~ 0.9 at the rest frame, this is
comparable to extinction levels found among other dark GRBs. The SED of the
host galaxy is explained well (chi2/d.o.f.=0.564) by a luminous (MB=-21.16),
low-extinction (AV =0, rest frame), and aged (2.6 Gyr) stellar population. We
can explain this apparent contradiction in global and line-of-sight extinction
if the GRB birth place happened to lie in a local dense environment. In light
of having relatively small specific SFR (SSFR) ~ 5.3 M_sun/yr (L/L_star)-1,
this also could explain the age of the old stellar population of host galaxy.
