You have to be creative and flexible if you are looking for 5 x J reward seats to and from Japan which probably means at least 1 or 2 stops or even flying to Seoul, spending a few days there and then taking an onward separate flight to Japan. Seoul to Tokyo or Osaka is only around 1hr 50 flight or so and there are often some great Avios deals if you want to fly on JAL or Virgin Flying Club deals if you prefer ANA or even Korean Air.

Also, are you planning on going during the Japanese summer? The humidity levels are intense and very uncomfortable - a lot of people really underestimate the heat between June and September, for example. I spent a month travelling around Japan in July 2018 and would never go at that time again unless you can spend most of your trip in an air-conditioned hotel, museum, a fabulous Japanese shopping centre or even just riding around on the bullet trains.

Record heat in Tokyo 2025