The archival discovery of a strong Lyman-$\alpha$ and [CII] emitter at z
  = 7.677
  We report the archival discovery of Lyman-$\alpha$ emission from the bright
ultraviolet galaxy Y002 at $z=7.677$, spectroscopically confirmed by its
ionized carbon [CII] 158$\mu$m emission line. The Ly$\alpha$ line is spatially
associated with the rest-frame UV stellar emission ($M_{\rm UV}$~-22, 2x
brighter than $M^\star_{\rm UV}$) and it appears offset from the peak of the
extended [CII] emission at the current ~1" spatial resolution. We derive an
estimate of the unobscured SFR(UV)=$(22\pm1)\,M_\odot$ yr$^{-1}$ and set an
upper limit of SFR(IR)$<15\,M_\odot$ yr$^{-1}$ from the far-infrared wavelength
range, which globally place Y002 on the SFR(UV+IR)-L([CII]) correlation
observed at lower redshifts. In terms of velocity, the peak of the Ly$\alpha$
emission is redshifted by $\Delta v$(Ly$\alpha$)~500 km s$^{-1}$ from the
systemic redshift set by [CII] and a high-velocity tail extends to up to ~1000
km s$^{-1}$. The velocity offset is up to ~3.5x higher than the average
estimate for similarly UV-bright emitters at z~6-7, which might suggest that we
are witnessing the merging of two clumps. A combination of strong outflows and
the possible presence of an extended ionized bubble surrounding Y002 would
likely facilitate the escape of copious Ly$\alpha$ light, as indicated by the
large equivalent width EW(Ly$\alpha$)=$24^{+5}_{-6}$ \r{A}. Assuming that [CII]
traces the neutral hydrogen, we estimate a HI gas fraction of $M({\rm
HI})/M_\star\gtrsim8$ for Y002 as a system and speculate that patches of high
HI column densities could contribute to explain the observed spatial offsets
between Ly$\alpha$ and [CII] emitting regions. The low dust content, implied by
the non-detection of the far-infrared continuum emission at rest-frame ~160
$\mu$m, would be sufficient to absorb any potential Ly$\alpha$ photons produced
within the [CII] clump as a result of large HI column densities.
