|Themis, the Titaness of divine law and order, was pissed off on how the police and their systems these days in the country were malfunctioning and rusty. Being a goddess heavily inclined to justice, she felt that her old customs and all that whatnot weren't working to help out in the modern mortal government. She decided against having another demigod child to do the job for her, as her offspring's blood would be stained by the injustice of mortals. With that, she called for Angelia, the goddess of messages and proclamation to help her out. She used the power of the word to give life to a fully-grown communication spirit to proclaim Themis' word and laws, while the Titaness herself used her powers to turn her offspring into the pure being of justice, deductive intelligence and judgment. She named him Katsuya, the same name of one of her partners from back then, who was a policeman.
Immediately after his creation, she sent him to the mortal world to perform his tasks. With the help of one of Themis' children, which was a lawyer, he was able to present himself as a police detective to assist in minor crime cases and helped out in solving them. Gifted with powers of communication and intelligence, he was able to detect criminals easily, travel long distances at a short time to collect data from witnesses and suspects, and deduce evidences quicker than most of the detectives with him in the case. In a short time, he was dubbed as the "Detective Prince", as well as "2000 IQ Killjoy Detective" for his intelligence and for being "killjoy" to the criminals he turned over to the police force. He served the police for ten years, ever since the year 2003.
However, on one bizarre murder case, it didn't involve humans; but monsters themselves, specifically hellhounds. Three people who had the Sight had long claw marks along their heavily injured bodies. Katsuya was tasked to report and investigate on the case, and he was confused, because the wounds on the mortals gave off a disturbing and unusual aura. He quickly set off to work, and with a little help from Themis, he was able to extract the answer. Promised to tell the truth, he did so in his report, and his colleagues were disappointed, since they reasoned that the whole thing was fictitious. He forced his words to reason out, only to be dismissed by the chief police officer, which only meant that he was kicked out of the case. Frustrated, he went back to Themis.
His creator felt that he needed a time off from solving cases. She felt that he had done a lot to help her out in her matters. So she asked him to go to Camp Half-Blood to relax for some time, until he made up his mind in entering the police force once again. As part of their agreement, Themis entitled Katsuya her loyal priest. Ever since then, he moved to the Bethel, and started to make himself at home at camp.