Jerome is a brave, determined and serious dog.He faces hardships with a calm attitude. Jerome is very attentive and often notices things the other dogs don't.Jerome accepts the responsibility of his actions. He was very devoted for his job and seems like he was slightly brainwashed by the training, as he believed the dogs have to bear any kind of treatment from humans without fighting back. It's been mentioned that his past as a contract killer has scarred his mind.He was ready to sacrifice himself and his minions for their mission.He greatly respects Gin, Smith, and Weed who are all ready to sacrifice themselves for others. He is incredibly loyal to Weed and sticks by him and  his actions no matter what.

Japanese voice for reference https://youtu.be/I5RIdicLLHU?t=2m26s