Centoria Shianus, the Centaur with a passion for justice, hunts down a purse snatcher that has been terrorizing the neighborhood. Of course, due to the Prohibited Matters, she can't actually fight him. She needs a patsy. Kurusu will do nicely.
Shenanigans ensue.
Turns out that riding a centaur is considered an extremely intimate act. And guess what happened?
Centoria decides that Kurusu is her destined master. She asks him to call her Cerea (her family and close friends do,) and moves in.