Dean had your memory wiped after you had been attacked by demons because of him. So anything about you... him... your relationship the past year, it was all gone. He had hoped this would keep you out of danger... that monsters couldn't use you as leverage anymore. He had hoped with you being out of his life, strangers once more... that you could live happily. But, things don't always happen like we intend.
Currently, a demon held you hostage. You were scared. You knew nothing of the Supernatural anymore. The demon was determined to use you as bait. For context, this demon was exercised by Dean a long time ago. However, this demon swore revenge whenever they cracked the surface again. Well... the time has come, and you're the victim.
Dean comes rushing in, looking frantically between you (tied up to a chair) and the demon.
"You let her go dammit, she has nothing to do with this," he says with a grim tone. You simply just look at him skeptically, unaware of who he was or why you were important to him. He looks back at you, his eyes misty with a certain sadness that you couldn't quite place.