This is a female. Taxonomy is complex with 15 to 20 described subspecies including several potential cryptic species. Birds in Japan are assigned to the subspecies E. s. pyrrhulina which is a winter visitor from breeding grounds in northern Honshu, Hokkaido and the Russian Far East. It is a pale subspecies with very pale unstreaked rump and faint breast streaking as seen in these images. It may be confused with female Pallas's Bunting which has gray lesser coverts, not rufous as visible here. It has occurred several times as a vagrant to North America in Alaska. Canon PowerShot SX60.
References:
Brazil, M.A. (1991) The Birds of Japan. Smithsonian Inst. Press.
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.
Copete, J.L. & Christie, D.A. (2019). Reed Bunting (Emberiza schoeniclus). 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 https://www.hbw.com/node/61900 on 8 April 2019).
Howell, S.N.G., Lewington, I. & Russell, W. (2014) Rare Birds of North America. Princeton Univ. Press