Usui is first introduced as a very bossy and strict person. He is very intolerant and demanding, forcing Yako and Neuro from the crime scene so that the police department would get all the glory when they solve the case. He also bosses Sasazuka around, though this is mainly because he holds a small grudge caused by an event that took place in the past. Usui also dislikes Higuchi for his unresponsible and laid-back behaviour.

Despite his behaviour however, Usui is otherwise a very responsible and reliable. He is very proud of the police force and is very capable as a leader, being able to motivate the entire force with just a speech. Sicks acknowledges Usui's abilities as well, stating he isn't special but he isn't normal either and that he is the type of person who will stand at the top when crisis arises. After the Histerrier case, Usui softens up with Yako and Neuro and begins trusting them, funding Yako's food during the HAL arc and taking directions from Neuro on Kasai's whereabouts.

Usui is secretly fond of cute things like stuffed animals and flowers, frequently blushing when it is brought up. He is also shown to like sweet things, getting angry at Sasazuka for serving him sugarless black coffee. In an omake, the artist states the car most suited for Usui would be a Mini.

(Source: Neuro Wikia)