I went to the Tokyo Apple Store (the one in Shibuya) to buy an iPhone 15, but ended up empty-handed. This was in early October, the 3rd if I remember well. The Apple employees there told me they sold out the stock they had early in the morning so, by midafternoon, they had nothing left.
I should caveat that I know nothing of phones, have no interest in phones except as a tool, and since I've got a now very old iPhone 6 I thought useful to change it for a newer model, especially as the price over in Tokyo was very good. In the end I didn't buy anything, and I don't know if the situation has gotten better.