As I described before, I am the Associate Certified Fundraiser, therefore, one of the areas of my particular interest is money, I mean, fundraising. 

Japan NPO Center kindly provides statistical information including the financial source of Japanese NPOs in English. 

Japan NPO Center "Nonprofits in Japan"
https://www.jnpoc.ne.jp/en/nonprofits-in-japan/size-and-scope/

In the section "Revenue breakdown of Specified Nonprofit Corporations", the circular chart shows 77% of revenue is "Program Fee" followed by 11% of grants/subsidies and 8% of donations.
You may not be able to understand the word "Program Fee". Me neither.  

As a matter of fact, these data come from the statistics of the Cabinet Office, the Government of Japan, which are all in Japanese. 
https://www.npo-homepage.go.jp/toukei

Data in "Revenue breakdown of Specified Nonprofit Corporations" is based on the statistic conducted in 2017 and "Program Fee" is an exact translation from the statistic.
So their translation is not vague. The word in the governmental statistic is vague. 

Fortunately, the Cabinet Office provides more detailed data in their following statistic conducted in 2020. 
In the statistics 2020, they separately analyzed 2 types of NPO.
One is an Approved (Certified) NPO and the other is a (general) NPO.
The statistic revealed a big difference between those NPOs in terms of the main source of income.

The most popular income source for general NPOs is the Membership Fee.
26.7% of general NPOs answered that Membership Fee as their main income source.
17.2% of NPO's is Fees from service users including sales of goods, and 16.8% of NPO's is Governmental Grants.

On the contrary, the most popular income source for Approved (Certified) NPOs is Donation (27%), followed by Membership Fee (19.5%), Commission Fee for governmental projects outsourced to them (15.9%). 

You may know that in Japan, you can receive tax breaks for donations only if you donate to Approved (Certified) NPOs or public interest incorporated foundations/associations. Maybe this is the reason.  

If you would like to know more about the difference between Approved (Certified) NPO and others, please see the section of "NPO Corporations and Certified NPO Corporations" in Japan NPO Center's website. 
https://www.jnpoc.ne.jp/en/nonprofits-in-japan/legal-framework/

Maybe I will write about it for myself as well, someday.