Note the barred undertail coverts. Sometimes included in the genus Porzana, this somber appearing species of eastern and southern Asia is extremely shy and rather poorly known. It is primarily a summer visitor here arriving in May, and not expected in February. The population on the main islands of Japan is assigned to the race Z. f. erythrothorax, the largest and drabbest subspecies. Canon PowerShot SX60
References:
Brazil, M.A. (1991) The Birds of Japan. Smithsonian Inst. Press.
Ripley, S.D. (1977) Rails of the World: A Monograph of the Family Raillidae. Godine, Boston.
Taylor, B. & Kirwan, G.M. (2019). Ruddy-breasted Crake (Zapornia fusca). 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/53664 on 2 April 2019).