Check Schengen Area on Wikipedia. You can see a picture that shows which countries are not required a visa to enter Schengen states :)
Yes, I know what the Schengen states are. All immigration rules are not the same for those states including who needs a visa and who doesn't (and what that visa entitles you to do in other Schengen states).
It doesn't surprise me that the website doesn't have info, that's why I also said you should call or email them. Immigration law is extremely complicated and Poland has one of the more difficult immigration systems to understand.
Look, here's why you need someone there. To understand immigration to a country in either the EU or Schengen (or both) you need to know the following:
-The EU, Schengen and that country's immigration rules. How that country applies the EU and Schengen rules (this does vary).
-Treaties that preceed the Schengen and/or EU agreement and are still valid.
-The immigration guidelines (which, if published at all, are generally very difficult to find).
-If it's something that falls under the embassy's purvue, the ebassies guidelines.
-And really, you need to understand the theory behind all of it to really have a good grasp of it.
And you have to be current on all of that. Those things change all the time. While people working in immigration get notification months or sometimes years before immigration laws/guidelines/ect change, the average person has to seek out these changes on their own. This is also why even people who work in immigration are wrong on occasion.
Unless you get lucky and run across a Polish immigration lawyer on a forum, a Japanese citizen who's fairly recently done what you're getting ready to do, or someone who's worked in the Japanese embassy in Poland, you're only getting a best guess. I've literally stood in an office with my Polish lawyer while he explained to the person handling my case what the laws were and for my previous permit
To give you a somewhat relevant example, some students in some Schengen countries can and do obtain a Schengen D type visa. That's because they do need it since that country doesn't have another form of permit to cover those cases. So, in France (IIRC) you'd need one and thus be able to obtain one. In Norway, since they have their own permits for students, you don't need one and thus can't obtain one. As an American in Poland, since there are other permits that cover me, I don't need one and thus can't get one. But, I don't know if that's because of the treaty or how Poland works in general for people that don't need a visa to enter. So my experience might be totally irrelevant.
Trusting random people on the internet to provide you with information is a very bad idea. That's the other reason I rarely comment on Polish immigration. With Norway, certain guidelines aside, I can provide links that back up everything. In Poland, I've gotten different answers from the same office.
If you don't believe me on the fact that Schengen rules are applies differently in different countries, look at the first sentence of imihelp.com
"Depending on the applicant's citizenship and/or residency or a few other rules, a Schengen visa may either be or not be required by all Schengen countries or some Schengen countries"
To back that up by the regulation itself (again, because of forum rules, can't link directly):
from COUNCIL REGULATION (EC) No 539/2001 of 15 March 2001
(8)In specific cases where special visa rules are warranted, Member
States may exempt certain categories of persons from the visa
requirement or impose it on them in accordance with public
international law or custom.
And, before you can dig into that lovely document, you need to start with Decision 1999/435/EC of 20 May 1999.
And that is why you have to be so specific when it comes to immigration EVEN to a Schengen country.