There are five recognised subspecies of the Blue Rock Thrush.
This is Monticola solitarius philippensis that occurs in Japan.
There is a proposal to split the Japanses subspecies into its own species: the Eastern (or Asian) Blue Rock Thrush (Monticola philippensis).
Top, Left & Middle: Nigishima, Mie Prefecture, Japan, 28 September 2018
Right & Last: Yunomine, Wakayama Prefecture, Japan, 30 September 2018