About yakuza in japan?

Question:

we all know that they are crime organization or a mafia so its simple to describe them that they are bad people...but somehow i heard that THEY HELPED people during WW2?

Answer:

Yakuza is supposed to be a criminal organization.
But they never rob banks, steal money or physically assault civilians on the street.
They are very well disciplined in accordance with their code of ethic; if they violate their rules, they would be expelled from the organization after losing couple of fingers off their hands.

Honestly, I have some friends who belong to a Yakuza group. One of them is my old playmate. We grew up together; we went to the same junior high school. Now, he is a big shot in his underground organization. But he doesn't look like Yakuza at all. We sometimes go out for a couple of drinks together. Nobody can recognize him. He exactly looks like an ordinary civilian who speaks very soft and polite language. He always stays calm and cool even if stupid drunk civilians try to pick a fight with him for some ridiculous reasons. He simply says, "I am very sorry if I hurt your feeling. I sincerely apologize. Please forgive me."
Not to mention, he never reveals his identity.
Not to mention, I never ask him what he is doing underground.

@Nightcap
As I said, I never ask him what he is doing. That will ruin our friendship. I still keep our relationship not because he is a Yakuza but because he was my old playmate long before he joined the organization. We used to go fishing together, played some pranks in our neighborhood, went to some strip theaters together when we were 14 years old, trying our best to look like over 18 by wearing our fathers' business suits and glasses. You know what boys are.
One day, he disappeared from our neighborhood. We didn't see each other for a long time until a few years ago. I don't know why and when he joined a Yakuza group. All I know is that he was managing a large number of "gaijin talent" clubs throughout Tokyo and Kanagawa prefecture. His job was to "help" girls from Russia, Ukraine and Philippines to "get married" with Japanese guys so that the girls can obtain permanent visa in Japan. Not to mention, all of them were fake marriages, a serious violation of Japanese immigration law. He was getting money from criminal organizations in those countries who were sending "gaijin talents" to Japan.
At some point of his "business," he must have been caught by Yakuza organization. Not only by Yakuza, he was caught by Japanese authorities and sent to jail for a few years. I know his group, belongs to Yamaguchi gumi, a largest Yakuza organization in Japan, is doing some profitable business underground; otherwise he is not able to keep his group. He wouldn't tell me what they are doing behind the scene. I wouldn't ask. But I know next time he severs contact with me, he is back in jail again.