Siberian rubythroat

 The Siberian rubythroat breeds in the People's Republic of China, Russia, and Hokkaido in Japan during the summer. (Cited from Wikipedia.)

And in the winter, it migrates south to Southeast Asia to overwinter.During the migration of birds, they fly south of Honshu in Japan. 

The lifespan of both wild birds was eight years from the time they were released to the time they were recovered, as per research materials from the Yamashina Ornithological Research Institute in Abiko City.（List of survival periods by species obtained from bird banding surveys: Top two records from 1961 to 2017.） 

I couldn't take their photo last year because they left before I could, but this year I was able to capture a male and female on my camera.It's a real struggle to find this wild bird.