Sometimes called Gray-capped Greenfinch, two subspecies breed in Japan. C. s. kawarahiba breeds in NE Hokkaido migrating south in the winter, while C. s. minor is a permanent resident replacing it as a breeder in the rest of Japan. C. s. kawarahiba can be identified in the field by its visible dark malar stripes lacking in C. s. minor which is otherwise similar to the nominate race of Eastern China but decidedly darker overall as seen here. Formerly included in the genus Carduelis but recent studies find greenfinches are a monophyletic group, genus Chloris which is not sister to other Carduelis species (Sangster et al. 2011).
Top two photos show males, bottom is a female. Canon PowerShot SX50 HS.
References:
Clement, P. (2017). Oriental Greenfinch (Chloris sinica). 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/61335 on 11 June 2017).
Clement, P., A. Harris, and J. Davis. 1993. Finches and Sparrows: An Identification Guide. Princeton Univ. Press, Princeton, N. J.
Sangster, G., Collinson, J. M., Crochet, P.-A., Knox, A. G., Parkin, D. T., Svensson, L. and Vottier, S. C. (2011), Taxonomic recommendations for British birds: seventh report. Ibis, 153: 883–892.
Zuccon, D., Prys-Jones, R., Rasmussen, P., Ericson, P.G.P. (2012). The phylogenetic relationships and generic limits of finches (Fringillidae). Molecular Phylogenetics and Evolution. 62 (2): 581–596