Ryuichiro Kuroda

Kumiko's grandfather. He is a kindly, wise old man who loves Kumiko very much, and is always there to support her and give advice. He took Kumiko in after her parents died. Though many rookies in the crime world might believe he runs a small branch of the Yakuza due to only having a few members, it is shown he is highly respected in the yakuza, and with a single command he could call upon thousands of members, as well as the few members are very strong and skilled at what they do.

(Source: Wikipedia)