  We report the detection of an extremely bright ($\sim$37 mJy at 1100 $\mu$m
and $\sim$91 mJy at 880 $\mu$m) submillimeter galaxy (SMG),
AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi),
discovered in 1100 $\mu$m observations of the Subaru/XMM-Newton Deep Field
using AzTEC on ASTE. Subsequent CARMA 1300 $\mu$m and SMA 880 $\mu$m
observations successfully pinpoint the location of Orochi and suggest that it
has two components, one extended (FWHM of $\sim$ 4$^{\prime\prime}$) and one
compact (unresolved). Z-Spec on CSO has also been used to obtain a wide band
spectrum from 190 to 308 GHz, although no significant emission/absorption lines
are found. The derived upper limit to the line-to-continuum flux ratio is
0.1--0.3 (2 $\sigma$) across the Z-Spec band.
  Based on the analysis of the derived spectral energy distribution from
optical to radio wavelengths of possible counterparts near the SMA/CARMA peak
position, we suggest that Orochi is a lensed, optically dark SMG lying at $z
\sim 3.4$ behind a foreground, optically visible (but red) galaxy at $z \sim
1.4$. The deduced apparent (i.e., no correction for magnification) infrared
luminosity ($L_{\rm IR}$) and star formation rate (SFR) are $6 \times 10^{13}$
$L_{\odot}$ and 11000 $M_{\odot}$ yr$^{-1}$, respectively, assuming that the
$L_{\rm IR}$ is dominated by star formation. These values suggest that Orochi
will consume its gas reservoir within a short time scale ($3 \times 10^{7}$
yr), which is indeed comparable to those in extreme starbursts like the centres
of local ULIRGs.
