So I think that the "other person" is Keira's father and since he's the one who can choose whom can retain memories, he chooses Keira! Loool It is only based on my understanding
spoiler:it is the father. the blonde hair girl was actually the evil who will destroy the world and so he decided to call for him to turn back time Yerenica <3
Omgggg I was right, thank you for your confirmation (≧∀≦)
So I think that the "other person" is Keira's father and since he's the one who can choose whom can retain memories, he chooses Keira! Loool It is only based on my understanding