First of all, you have to be able to operate patent databases, such as soopat or the patent information service platform of intellectual property publishing house ... (There are other databases, too numerous to mention, and insufficient preparation).
In the table search function, find a field named "country code" and enter JP (this step represents Japanese patent application in China).
Then according to the technology you want, enter the appropriate keywords in the field of "abstract" or "claim".
Not surprisingly, there should be many patents listed, unless there is something wrong with the keywords you use, and then look at them one by one and find the patents you want. Congratulations! ! ~~~
If you have clear information about the patentee or patent application number, you can directly enter the application number or patentee in the patent database mentioned above.