She was hit by a speeding car. He rushed to the hospital. When she woke up, she realised her amnesia, and she wanted to know. She wanted to know everything. Everything that happened before she got hit, even when it hurts to be wih him. She knows he's someone special, but who exactly is he? Her head hurts when she's with him. but she wants to know. She doesn't care about her head.

It hurts. It hurts him that she doesn't remember. It hurts him that he can't cradle her like before. But what can he do? He can see she's hurting now and he wants it to stop. He wants her to stop trying to put the puzzle pieces together. he wants her to stop hurting her head by being with him

Inspired by Boyfriend's IYAH, the part where they grab their head because it hurts. And also I've heard that IYAH is what Koreans say when they have a headache.