Who Am I?

According to the first book(tomura shigaraki x reader), they all thought that Y/n died but actually she is still alive but it was a long time to recover because the bullet went through her heart.When shigaraki go shopping wearing his hoodie, he saw Y/n. He called out Y/n and Y/n looked at shigaraki.
"Y/n, You're still alive?!"
"Who are you?"