The Grey Angel (Attack on Titan x OC)

"See the sea together. That sounds nice" he said.
"Then let's make a promise" I said and he looked at me. "That we're going to see the sea together"

At 4 years old, Nora was left alone by her father at an orphanage.
She got adopted by Marie Sato, a woman who had just lost her husband.
Nora's strange appearance was what got Marie's attention. What girl has dark grey hair and such dull blue eyes?