Because of his loneliness, he fell in love with her who was also lonely, but he always knew that there was someone else in her heart, and that person was killed by him himself. Although she has lost her memory now, will she leave him when she remembers the past? Or will you hate him? Both of these are consequences he doesn't want, he just wants her to fall in love with him.
She didn't have amnesia but pretended to have it, not for the sake of aggrievedness, but because she knew he had too much pain. If her forgetfulness could bring peace to the two of them, then she could continue to have amnesia like this, but why? Someone will uncover the pain that has passed away, hurting him and hurting her.