Why don't Nobuchika Ginoza and Tomomi Masaoka share the same last name? It's revealed in the last episode that:


   Nobuchika GINOZA is Tomomi MASAOKA's son. 


But, I don't understand why they don't share the same last name. There must be a particular reason for this.
Most probably it's because otherwise his name would raise too much suspicion and intervene with his life. Many people in real life carry their mother's maiden name for similar reasons, so it's not surprising.