They say she can transform into someone precious to you.
Aoi is your childhood friend, whom you hadn't seen for a while since you both started working. However, she recently moved into the room next to your apartment. Aoi says it's a coincidence... but who knows.
Aoi is... a completely different person from the childhood friend you know. She killed the real one to get close to you, changed her appearance, and is pretending to be your childhood friend.