In the category of the IUCN Red List: Least concern
Category of migrant to Japan: Passage,winter migrant
Bluethroat(Ogawakomadori)was a vagrant bird with a few sightings before in Japan, but as an research advances, records increase and are done with a bird in passage rare now or a winter bird. There are many records in the islands part of the Sea of Japan side.( Quote from a Japanese sentence of Wikipedia)