I'll explain the requirements in this response and describe the necessary documents in my next response.

1. The applicant's behavior must be of a high standard. This means s/he should not have been involved in any crimes or tax evasions.

2. The applicant needs to have enough assets or skills to be able to live independently in Japan. His/her living situation must not be a burden to the public and s/he should be able to continue living a stable life in the future, considering his/her assets and skills. It is believed that applicants must have a specific amount of savings to obtain a permanent visa, but this is not correct.

3. The applicant's permanent residence meets Japan's national interests. This means your permanent residence must be recognized as being useful for Japanese society and the economy.

4. The above are general requirements. The length of stay is one of the individual requirements. If you are a spouse or a child or an adopted child of a Japanese, or a permanent visa holder or you are a recognized refugee or resident, you may apply for the visa with a duration of one year, three years or five years. However, this generally requires 10 years stay in Japan. In your case, you will be able to apply in one year's time.

5. In addition to the personal requirements, it is necessary that you are currently holding the longest term visa. As you have a three-year visa, you are already qualified.