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We present deep Keck/MOSFIRE near-infrared spectroscopy of a strong Lymanalpha emitting source at z=6.1292, HSC J142331.71-001809.1, which wasdiscovered by the SHELLQS program from imaging data of the Subaru HyperSuprime-Cam (HSC) survey. This source is one of five objects that showunresolved (<230 km s-1) and prominent (>10^44 erg s-1) Lyman alpha emissionlines at absolute 1450 angstrom continuum magnitudes of M1450~-22 mag. Itsrest-frame Lyman alpha equivalent width (EW) is 370+/-30 angstrom. In the 2hour Keck/MOSFIRE spectrum in Y band, the high-ionization CIV 1548,1550 doubletemission line was clearly detected with FWHM =120+/-20 km s-1 and a totalrest-frame EW of 37-5+6 angstrom. We also report the detection of weakcontinuum emission, and the tentative detection of OIII] 1661,1666 in the 4hour J band spectrum. Judging from the UV magnitude, line widths, luminosities,and EWs of Lyman alpha and CIV, we suggest that this source is areionization-era analog of classical type-II AGNs, although there is apossibility that it represents a new population of AGN/galaxy composite objectsin the early universe. We compare the properties of J1423-0018 tointermediate-redshift type-II AGNs and CIV emitters seen in z=6-7 galaxysamples. Further observations of other metal emission lines in the rest-frameUV or optical, and X-ray follow-up observations of the z=6-7 narrow-linequasars are needed for more robust diagnostics and to determine their nature.

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). XIV. A Candidate Type-II Quasar at z=6.1292