The Gift of Memory (Armin Arlert x Reader|Modern AU)

Every day, Armin Arlert spots a mysterious girl at the old playground that has practically been abandoned for over a decade. He always passes her on his way to and from school. And something about that girl always invokes his curiosity.
Maybe it's the fact that she's never in school.
Maybe it's the fact that she's there every day.
Or maybe it's the sad smile and wave she only returns when given.
The boy always wanted to say hello to her, but he never even managed to build up enough courage to speak to her. Just a simple smile and wave. To be polite is all.
But once they finally meet, something about her seems soft and melancholic. As he learns more and more, the poor girl that possesses the gift of memory seems even stranger than before.