https://services.digital.go.jp/mynumbercard-iphone/news/10c42297159b33349de8e/
「iPhoneのマイナンバーカード」の提供を開始しました
Apparently since JPKI is more secure™ than the ISO standard, you can’t add the card to your watch. I imagine it’s similar with eIDAS compared to ISO, but it would be interesting to see support added as a native alternative to the EU wallet apps