Wikipedia: Japanese naturalization
To begin with, the first two statements in the first paragraph are inaccurate:
- "Naturalization in Japan requires the applicant to renounce their current citizenship(s) after the naturalization takes place."
This statement is only true for a minority of cases (i.e. the United States). For most countries (the most common: Republic of Korea and the People's Republic of China), and even many western countries like the United Kingdom, you give up your previous nationalities as the last part of the application process right before you are naturalized to Japanese. - "Japanese government does not have strict rules for naturalization process"
I think the author is trying to say that because the documentation from every country, which is used to change your citizenship, is different, and because the metrics used to determine if a candidate has adequate means to support a livelihood is not an exact number, that the rules are not "strict."
In the second paragraph, the article claims that "the applicant must have been living in Japan for 5 years at the time of application (3 years if married to a Japanese national)." This is a very simplified version of the criteria difference between 普通帰化 (normal naturalization) and 簡易帰化 (simplified naturalization). It's possible to only need to live in Japan for one year. There are many different types of connections to Japan that will cause the continuous physical presence requirement to be shortened. Marriage is one of them. And just being married is no guarantee that the length of time will be three years. It may be five, three, or one year, depending on the length of time one is married. Also, the definition of "living in Japan" needs to clarify that it means continuous years being physically present in Japan, with no more than 100 days continuous and 150 days total per year outside of Japan.
The "booklet" that the article is referring to is the 『帰化許可申請のてびき』 ("Naturalization Permission Application Guidance"). This is not always given out on the first visit, but is usually received by the second visit. They may give you a smaller pamphlet explaining the process the first time (or they may not).
While the booklet does "[explain] every needed document and [process]", it does not explain which of these documents and processes will apply to your particular situation, which is why the case worker is needed and will provide you with a more specific list of documents after assessing your situation.
The article says there are three stages. This is somewhat rough. A better understanding of the process is the flowchart at the back of the pamphlet they sometimes provide, which breaks the process up into nine phases.
The article says there may be a written test at the "elementary school second [2nd] grade level." However, if there is a written test, most agree that it is at a third (3rd) grade level.
The exact list and number of 漢字 {kanji} (Japanese sinograms) that a school in Japan with credentials from 文部科学省 — MEXT (Ministry of Education and Technology) — teaches is predetermined. This is why one can generally assess the particular grade level a written Japanese test focusing on vocabulary and characters is targeted at.
Finally, the article ends with, "the applicant will be called by their interviewer about the decision". While this was the case for me, my case officer did indicate that I may receive notification by mail, by phone, or both.
From reading the article, it's obvious that it was written based on the account of one or a few individuals who had gone through the process. There is nothing fundamentally unbelievable or false in the article. However, the requirements described, with the conditions and processes, only applied to a particular person (ex. An long-term married to Japanese American :: three years of residency and renouncing afterwards), and not to the majority of cases that 法務省 (the Ministry of Justice) processes.
