At what point does the title of The Reader become clear. Who is The Reader in Bernhard Schlinks novel?

Bernhard Schlinks novel The Reader poses the question who is the reader is it the narrator or are there others in the story with an equally compelling claim to this roleAt what point does the title of The Reader become clear. Who is The Reader in Bernhard Schlinks novel?
I thought the answer became clear about a third of the way through when we learn the narrator, Michael, was reading to his older lover Hanna before they had sex. But then further along (but earlier in chronological time) there was another reader, again a young person reading to Hanna, but this time in a concentration camp. Ultimately it seems that perhaps Hanna is the reader. Years later, toward the end of the story, her secrets have unfolded and through Michael again filling the role of the reader in her life, Hanna herself begins to read. Through reading it seems she comes to a greater understanding of the consequences of her past decisions and relationships.