Reiji Mitsurugi is an esteemed prosecutor and an old friend of Ryuuichi Naruhodou. During his first four years as a prosecutor, he had a perfect win record, and he was a ruthless man who would do anything to get a guilty verdict for the defendant. He was adopted by his mentor, Manfred Von Karma, after the death of his father in the DL-6 case.

Mitsurugi is generally seen as a snob due to his skeptical, ruthless and generally aloof nature that differs little between everyday life and the courtroom. However, he has a strong sense of right and wrong, and acts only in ways that he believes are fair and just.

Generally, Mitsurugi is calm and level-headed when talking with people, although he does tend to come off as a little cold and, sometimes, rather condescending.

In court, Mitsurugi usually has the trial precisely planned out, ensuring his victory. Because of this, he tends to become easily ruffled with anything that does not conform to his plan. In particular, he tries to stick to standard courtroom proceedings, trying to make the witnesses state their names and professions, although he regularly has a great deal of difficulty with this task due to the often rather eccentric characters called as witnesses in his cases.