Do i need a visa for an unpaid internship?

Hello, I'm planning to do an internship in Tokyo around September
I intend to stay for less than three months and since I'm not being paid I suppose I don't need a visa.
Now this is where it gets confusing because the embassy tells me I need a "Cultural Activities" visa since it is work at an engineering company, however, the consulate at my city tells me I don't need any.

The embassy suggested that I request the inviting company to ask at the Immigration Bureau in tokyo if I need to have a visa

If possible I'd like to skip the 1-2 months it takes to get the Certificate of Eligibility plus all the problem of waiting for the company to make the paperwork

What do you think? do you think is risky to go without visa and just say I'm doing unpaid business or do I go for the visa, keep in mind that I'm short on time

Thanks in advance

You can NOT work on a tourist visa, that visa is only for people who are traveling, even if you won't get paid that doesn't mean you can use tourist visa, like the embassy said you need another type of visa

Yes, go ahead. Any unpaid activity (that doesn't otherwise violate Japanese law) is fine on Temporary Visitor status.

(The fact that the person above said "tourist visa" demonstrates he doesn't have a very good knowledge of Japanese immigration matters.)

http://www.eriw-office.com/category/1428400.html#Q28
according to the above website,(in Japanese)

UNPAID internship
more than 90 days = you need to get a "Cultural Activities" visa =「文化活動」ビザ
less than 90 days = a "short-term stay" visa.=「短期滞在」ビザ
if you come from the countries as listed below, your "short-term stay" visa application will be exempted.
http://www.mofa.go.jp/j_info/visit/visa/short/novisa.html

the website says:
no social insurance(no health insurance) will be provided.

(The fact that the person above said "tourist visa" demonstrates he doesn't have a very good knowledge of Japanese immigration matters.)

I wouldn't rely on this as an "indicator". Even knowledgeable people commonly use "tourist visa" instead of "status of residence" as it is easier for non-knowledgeable people to understand.

Thanks for the quick replies.
So, what do I say when I arrive at the airport?

Is it okay if I say this?: "XXXX company invited me as an intern, I will be responsible for all my expenses, I will stay less than 90 days and they won't pay me"

Thanks again

Would it be better to tell the staff that you are on vacation instead?