Tatsuya is a senior student enrolling in Seven Sisters High School in Sumaru City. He has an older brother named Katsuya Suou, a police detective, as well an unnamed father. Tatsuya has brown hair worn long with a center part (called a newsboy haircut), brown eyes. A distinct characteristic of his present in both Innocent Sin and Eternal Punishment is his habit of flicking the engraved Zippo lighter Jun gifted to him as a child open and closed.