When asked if he understood he would never be released from prison, Ariel Castro said: "I do understand that, your honor."
He added, "I knew I was pretty much going to get the book thrown at me."
The deal comes more than a month after a statement issued on behalf of the women said they were "hopeful for a just and prompt resolution" and had "great faith in the prosecutor's office and the court."
More top news
In her message Theresa May praised the "inspirational bravery" and "unbreakable spirit" of Mancunians in the wake of the blast.
ITV News has obtained exclusive footage of the moment armed police raided a house believed to be linked to the Manchester suicide bomber.
The Manchester Evening News set up a JustGiving page asking people to support the families of those affected by the suicide bombing.