When he was young, he was in the same college as Kyougokudou and Sekiguchi. Despite being their senior, he quickly became friends with Kyougokudou thanks to their common natural weirdness. He is also a childhood friend of Kiba.

During the war when he was a child, Reijirou practically lost his sight that resulted in gaining in him a special ability to see the floating memories of the people around him. In order to exploit this gift, he became a private detective at the "Rose and Cross" agency he founded himself. He had a hard time remembering people's names and often teases Sekiguchi for looking like a Turtle.