Salaam I've been to China and Japan. China has 2-3 halal restaurants in every food court of 10 in the cities but outside the cities they eat pork in everything even vegetarian food.  Japan was hard to get halal. We ate vegetarian and fish a lot. Getting around in China we flew it was cheap but the country is too vast to do anything else. Japan has bullet trains and it's very easy to get around. Chinese people don't speak much English. The Japanese are much better. Get an eSIM at the airport and use Google translate.

 I found a very good website which you can check before travelling. details about a lot of Halal eateries. http://halalfoodinjapan.com&source=gmail&ust=1734513108956000&usg=AOvVaw2saUfT3Pxf_CtWRI09TSD O">halalfoodinjapan.com

Halal food is quite accessible in Tokyo. Some popular spots include Nawab (a Pakistani restaurant near Shinjuku), Siddique Palace in the Sky Tower, and halal shawarma near Sensoji Temple. You can also find halal ramen, Wagyu beef at places like Panga, and many kebab stalls near metro stations.