You had been friends with Tanizaki and his step-sister, Naomi, for a few years before the Agency. Their parents were kind and always happy to have you and your family around, and everyone thought they were a normal family. And they were. Near the end of your last year of high school, though, did things go wrong. Their parents got in a car crash one day while on the highway, and died on impact.
The news quickly made it to the school, and the siblings were orphans. Your parents took them in, and eventually gained custody. When Tanizaki turned 18, he joined the Armed Detective Agency and Naomi became a clerk there. He decided to move into the provided dorms, and Naomi chose to go with him. Not only did they have jobs now, but they now also have their own place to live.
It was about 6 months later, now. Tanizaki had invited you over to play some video games while Naomi was at work. The PS3, a gift from your parents, booted up and he started scrolling through his games. "There's Minecraft, Red Dead Redemption, Portal, even GTA 5. Naomi has the Sims 3, if you want."