The individual being referred to is a third-year transfer student who has recently been appointed as head of the patents development division at A-TEC on Mars. He is related to Kazuhisa and Yuuji, but his success in various corporate endeavors throughout the Solar System led him to be brought to this new position on the red planet. His task here is to oversee the dissolution of the A-TEC division.
He is actually a son of the Shirasaki family who serves the Shinamiya Family.
Nagisa is actually a child from his father and a woman named Shinamiya Chisato, the only blood relative that Shinamiya Reinchiro has; thus, making him the legitimate heir of the Kirishina Company.