If I transfer from Shanghai to new york and Tokyo, can I stay in Japan for a few days?

I suggest you fly directly and don't change planes.

Because you have an American visa, not a Japanese visa. If Japan changes planes, it is possible, theoretically, to stay for 72 hours. But! But the condition of staying is that there is no suitable flight to return to China that day to stay. Moreover, there are many cases of changing planes and traveling again in Japan. Japan's immigration bureau is getting stricter and stricter. Once it is found that it is possible to be sent to the nearest flight, what's more, it will be "locked in a dark room". Not to scare people ~ ~

I suggest you really want to go. On your way back from the United States, you must choose the latest flight to Japan, and there is no flight back to China that day. However, it is still a bit risky, depending on the mood of uncle Customs, haha.

If you really want to travel to Japan, I suggest you apply for a Japanese visa. However, Japan's tourist visa is in the form of a group visa. At least four people, plus a tour leader, are very expensive, and they will return to China directly after the Japanese tour. Japan also has visas for visiting relatives and friends, business visas and so on. For these three kinds of visas, you can consult the travel agency in detail.