Stejneger's Stonechat Saxicola stejnegeri (a recent species split, formerly listed as either Saxicola torquatus stejnegeri or Saxicola maurus stejnegeri), male. Japanese name: ノビタキ. They are summer visitors in Japan, presumably newly arrived.
Hi Resin, As always, your confirmation and information is greatly appreciated. My field guide did not have the Stejneger's part of the name. Only stonechat (no-bitaki). I had gone to the nearby river to check out the mute swan nest, so the stonechat was an added plus and a new bird for me! Good birding to you this spring. Kawasemi