Michael feels guilt about Hanna nearly during the whole story. This feeling starts when she feels aggravated by a trivial conflict and Michael takes all the blame on himself: “She let me in, and I said the whole thing was my fault. I had behaved thoughtlessly, inconsiderately, unlovingly. I understood that she was upset. […] In the end, I was happy that she admitted I’d hurt her.”
Similarly, Michael believes he had betrayed Hanna. When Hanna goes away one day after he ignored her at the public pool, he asked himself, “Why hadn’t I jumped up immediately when she stood there and run to her! This one moment summed up all my halfheartedness of the past months, which had produced my denial of her, and my betrayal. Leaving was her punishment.”
The feelings of guilt disappear over time. When Hanna is convicted of her involvement in the SS, Michael even feels guilt:
“And if I was not guilty because one cannot be guilty of betraying a criminal, then I was guilty of having loved a criminal.”
Even as Hanna ends up dead because of suicide, Michael asks, “In the first few years after Hanna’s death, I was tormented by the old questions of whether I had denied and betrayed her, whether I owed her something, whether I was guilty for having loved her. Sometimes I asked myself if I was responsible for her death.”
So his feeling of guilt pull throughout the whole book and they are always the same motives: betrayal, denial, and at the end, Hanna’s death. Ten years after Hanna’s death, Michael frees himself from this guilt that accompanied him most of his life by writing the story down.