The letter Peter wrote to MJ at the end of Spider-Man: No Way Home is revealed in Spider-Man: Brand New Day
Hi, my name is Peter Parker, and you don't remember me, but I have something to tell you that's going to sound crazy. But it's the truth, and I know you're going to believe me, because you're very good at telling when I'm lying. We used to know each other.
We were together. But something bad was going to happen to the world. And the only way to stop it was to make everyone forget me, including you. Because I'm not just Peter Parker. I'm Spider-Man.
And sometimes, Spider-Man has to do the hard thing. Even if it breaks Peter Parker's heart. Maybe I'll never read this to you. Maybe I'm just writing this for me. Maybe that's my responsibility, to live alone with the truth.But the truth is I love you.
And I hope that deep down, something inside you remembers you love me too.”
English
