Whilst I not sure exactly what this is, having seen the bird (rather briefly), this is not a Rufous-tailed Robin. In the field the entire upperparts are rather uniform in colour and are a rich reddish brown. From behind it looked like a typical Japanese Robin, and of the hundreds of Rufous-tailed Robins i have seen over the years, I have never seen one with such rich uniformly toned upperparts.
Likewise, the rufous tones to the head and ear-coverts are wrong for Rufous-tailed Robin, and the scaling below is actually at the extreme end for this species yet it lacks the blackish submoustachial typical of well-marked birds. The flanks are never so uniformly grey in Rufous-tailed Robin and finally it lacks a short supercilium between the eye and the bill which many show.
That said, the pale throat and extensive scaling is totally wrong for Japanese Robin.
