I looked it up, it's like... You know how in the yakuza, you call a senior member aniki and your boss is your oyaji, and it's like a family? Some guys join the yakuza together, and they swear an oath to each other, to have each other's back.

[ He hasn't remembered that Nishiki is his... but after remembering him as a kid, it's not hard to put two and two together. ]