We were not expecting this species in February. It is a rare visitor to southern Japan in Winter although it breeds commonly as far as northern Honshu. The Japanese population is assigned to the subspecies B. s. amurensis which breeds from the Russian Far East, through northeast China, Korea and Japan and migrates to Southeast Asia. Digiscoped Panasonic Lumix LX5 | Nikon FieldScope III | 30X hand-held no adapter
References:
Brazil, M.
Martínez-Vilalta, A., Motis, A., Christie, D.A. & Kirwan, G.M. (2019). Green-backed Heron (Butorides striata). 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/52704 on 29 March 2019).