Being the Chief of Police of Sakurami City, Kurusu has absolute command of the Police force to do his bidding. The fact they can fight for him without knowing of his Diary or his participation of the game shows his complete and absolute authority over them.
At first the police forces are an ally to the protagonist due to Keigo Kurusu originally wanting to just minimise the damage of the game. They were of some help during the Minene boming incident. Keigo helps during the cult massacre and covers things up after the Reisuke Houjou battle. But after the fight with the Karyuudo dogs, Kurusu kills Karyuudo. This is the turning point where he starts to become antagonistic. Then keigo has Yukiteru and Yuno arrested for the murder that he committed. He plays Russian Roulette with Yuki causing Yuno to come to his rescue injuring him in the process. This Gives him an excuse to send his men after them but Nishijima is not fond of this and helps them escape though Yuki has to non-fataly shoot a detective.
Masumi Nishijima (西島 真澄, Nishijima Masumi) is the chief investigator of the Sakurami Police force and the subordinate of Keigo Kurusu. Although he turns against him after learning the truth about his actions, becoming the new chief of the police force