Sakura is Key's best and only friend from childhood. In fact she's her step sister, as her father had a hidden relationship with Toyoko Mima. She usually shows a quite easygoing and simple personality, but on the inside she's very insecure and confused. And these unbalanced traits often rise up in her relationship with Key, as she often taxes Key with trivialities and acts somehow hysterically. But somehow she always end helping and caring about Key.