This is a male showing black chin. HBW splits this race into a separate species which they call Masked Bunting (Emberiza personata). This treatment is based on the controversial Tobias system which gives a score of nine based on "objective" criteria. Under this system, a score of seven or more raises distinctive subspecies to full species. Perhaps more compelling are several recent studies showing the genetic distinctiveness of this taxon (see references).
However, this split has not yet been accepted by Clements/eBird, IOC or H&M4 all of whom treat E. s. personata as one of three subspecies of the Black-faced Bunting with two other races found on the Asian mainland. Regardless of taxonomy, the population in Japan differs markedly from the others by its yellow throat and breast as seen here. Mainland birds usually have a full gray hood. Canon PowerShot SX50 HS.
References:
Byers, C., J. Curson, and U. Olsson. 1995. Sparrows and Buntings: A Guide to the Sparrows and Buntings of North America and the World. Houghton Mifflin, Boston.
del Hoyo, J. & Collar, N. (2017). Masked Bunting (Emberiza personata). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/1344137 on 13 June 2017).
Päckert, M., Sun, Y.-H., Strutzenberger, P., Valchuk, O., Tietze, D.T. & Martens, J. (2015) Phylogenetic relationships of endemic bunting species (Aves, Passeriformes, Emberizidae, Emberiza) from the eastern Qinghai-Tibet Plateau. Vert. Zool. 65(1): 135–150.
Saitoh, T., Sugita, N., Someya, S., Iwami, Y., Kobayashi, S., Kamigaichi, H., Higuchi, A., Asai, S., Yamamoto, Y. & Nishiumi, I. (2015) DNA barcoding reveals 24 distinct lineages as cryptic bird species candidates in and around the Japanese Archipelago. Mol. Ecol. Res. 15(1): 177–186.
Weissensteimer, M.H., Koblmüller, S. & Sefc, K.M. (2014) The Emberiza spodocephala subspecies complex: new insights into taxonomy and phylogeography. 26th International Ornithological Congress 2014, Tokyo, 18-24 Aug 2014.