As a kid, Nagi was ostracized by those around him because of his telekinetic abilities. Following an accidental killing of his mother and erasing the memory, Nagi was taken in by Brad Crawford from Schwarz. To better understand his ESP powers, Crawford left him under the care of Sister Kaoruko Amamiya, a nun who specialized in treating traumatized children. Ken Hidaka also stayed at her orphanage after his mother's death. However, it turned out that Sister Amamiya was using the kids living there to commit crimes through hypnosis she implanted during counseling sessions. While visiting an old friend from the orphanage, Ken encountered Nagi and later learned of Weiss receiving a mission to target Sister Amamiya. It was Ken who ultimately killed the nun. Witnessing the murder left Nagi devastated, causing him to make the church collapse using his telekinetic powers. From that point on, he vowed to kill Weiss and harbored a specific hatred for Ken. Afterward, Crawford rescued him and sent him to Germany's Rosenkreuz facility for further study. Now Nagi works with Schwarz to seek revenge against the world for how he was treated as a child. He is somber and embittered towards life and society.