(Y/N) is Online

Paperjam, Chara, Undyne, Fresh, Nightmare, Error, and Cil get a notification on their phones. (Y/N): You remember me, don't you?

The Society of Imaginary Friends (Book 1 of The Conjurors Series)

Belief is a powerful magic. Valerie Diaz has a power that she can't contain, and it's killing her. Bounced between foster homes and the streets, she only has time to concentrate on staying alive. But a visit from the imaginary friend of her childhood opens a world of possibilities, including a new life half a universe...