http://www.thedailybeast.com/blogs-and-stories/2011-03-18/japanese-yakuza-aid-earthquake-relief-efforts/

The Inagawa-kai has been the most active because it has strong roots in the areas hit. It has several "blocks" or regional groups. Between midnight on March 12th and the early morning of March 13th, the Inagawa-kai Tokyo block carried 50 tons of supplies to Hitachinaka City Hall (Hitachinaka City, Ibaraki Prefecture) and dropped them off, careful not to mention their yakuza affiliation so that the donations weren't rejected. This was the beginning of their humanitarian efforts. Supplies included cup ramen, bean sprouts, paper diapers, tea and drinking water. The drive from Tokyo took them twelve hours. They went through back roads to get there. The Kanagawa Block of the Inagawa-kai, has sent 70 trucks to the Ibaraki and Fukushima areas to drop off supplies in areas with high radiations levels. They didn't keep track of how many tons of supplies they moved. The Inagawa-kai as a whole has moved over 100 tons of supplies to the Tohoku region. They have been going into radiated areas without any protection or potassium iodide.

The Yamaguchi-gumi member I spoke with said simply, "Please don't say any more than we are doing our best to help. Right now, no one wants to be associated with us and we'd hate to have our donations rejected out of hand." [...]

There is an unwritten agreement amongst the police and the yakuza groups that is acceptable for them to perform volunteer activities during a crisis but not to seek publicity for it. Before the crisis the police were cracking down severely on the yakuza and any activity placing them in a heroic light might make the police look foolish. So they have been very quietly doing their part. It is not that the yakuza are not PR savvy, as is evidenced by their careful control and limited appearances in six fan magazines (three monthly, three weekly) that write of their exploits; it is that right now they care more about getting the job done than getting credit for it. As one members said, “There are no yakuza or katagi (ordinary citizens) or gaijin (foreigners) in Japan right now. We are all Japanese. We all need to help each other.”