Kenichi Yabuki
About
Kenji's estranged father, who appears only through flashbacks. He left the family while Kenji was still a child, returning irregularly to extort money from Kenji's mother Mineko; because Kenichi became violent during these incidents, Mineko was never able to formally divorce him. 20 years prior to the events of the series, the Yabuki family became aware that he was still alive after receiving notice that he had applied for welfare.
In chapter 64, Kenji is notified by the police that Kenichi has died.
(Source: Wikipedia)