The Immorals Jokei Kazoku: Inbou

An evil politician Arimori Kamoshige have been a local governor for 40 years,. Abusing his power, he has gained wealth and women. The protagonist’s father has managed Arimori’s black money as a right hand person, but later, he was expelled being charged false crime. He got discouraged and called his runaway son, Tatsuya. He asked Tatsuya his revenge on Kamoshige. Soon his father died, and Kamoshige hired Tatsuya as the third secretary. However, Kamo also died 3 months later. Just before his death, he changed the pass code of a safebox which hidden black money was in. Then, the power balance of Arimori Family changed. The person who obtains the hidden money will get become the next ruler. While Arimori Family is conflict for the hidden money, Tatsuya begins his revenge. (Source: AniDB)