This is primarily a winter visitor to southern Japan. This smaller East Asian subspecies has its face and throat fully feathered unlike the nominate race in Europe. Brazil (2018) treats these birds as a separate species under the name Eastern Rook, but this treatment not widely accepted. These are adults based on the pale base to their bill. Juveniles are similar but have an all black bill. Highly gregarious they nest colonially in rookeries, a term that has come into general use for colonial birds. Canon PowerShot SX60.
References:
Brazil, M. (2018) Birds of Japan. Helm Field Guides
Madge, S. & Burn, H. (1994) Crows and Jays: A Guide to the Crows, Jays and Magpies of the World. Houghton Mifflin, Boston.
Madge, S. (2019). Rook (Corvus frugilegus). 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/60784 on 2 May 2019).