It was totally by accident. I was browsing one of those top 10 list websites and they had a list of infamous crimes committed by the yakuza. One entry was on the Kudo-kai. It mentioned that they were from Fukuoka, and that they had a penchant for killing civilians (unlike the majority of yakuza groups), and suddenly something clicked and I thought "minagoroshi!" So I looked it up on Wikipedia, and the logo was right at the top of the page.
Then I started browsing organized crime logos for fun.
Oh, another interesting fact about the Kudo-kai: In 2000, they attacked the home of Prime Minister Shinzo Abe (then a member of the House of Representatives) with molotov cocktails, apparently because one of his aides failed to pay a bribe. To me, this is almost inconceivable...obviously these are some BAD m-f'ers.