I believe it is the case that US (at least) iPhones work as IC cards in Japan
Source - I’m sitting in Kyoto right now having travelled all over Tokyo and then on to Kyoto using only my phone to interact with Japan Rail. Verified with two 16Es and a 12. In fact we were able to add the Suica cards to our phones and charge them fromApplePay while still stateside. That let us skip the Welcome Suica line at Haneda and go straight to the monorail. Highly recommended
Source - I’m sitting in Kyoto right now having travelled all over Tokyo and then on to Kyoto using only my phone to interact with Japan Rail. Verified with two 16Es and a 12. In fact we were able to add the Suica cards to our phones and charge them fromApplePay while still stateside. That let us skip the Welcome Suica line at Haneda and go straight to the monorail. Highly recommended