All that is known that his family is rich and he was spoiled growing up.
Kuruma first appears in this arc, reporting that he and Kō Murakami have arrived on the scene to take down a trion soldier. When a Rabbit emerged from the wreckage he was avised to fall back and rejoin with the other B Units with Taichi Betsuyaku while Murakami fought them there.
They met up with Azuma's Unit and Kakizaki's Unit, and were planning their next move when they noticed a Humanoid Neighbor was attacking. The group teamed up with several A rankers and Kuruma was praised on his acting skills to bait to lure Lamvanein into a trap. He wasn't acting though.