The First To Die at the End is the prequel to They Both Die at the End (2017). Both novels are written by Adam Silvera, and they tackle similar themes relating to the Death-Cast service begun by Joaquin Rosa. In each novel, two gay teenagers are the protagonists, and the storyline follows those boys as they progress through one day. The First To Die at the End is different in that only one of the lead characters—Valentino—has received a call from Death-Cast, while both boys in They Both Die at the End are Deckers.

Silvera also alludes to the main characters of They Both Die at the End, as each makes two appearances in this novel. Rufus Emeterio is the son of Dr. Emeterio, who cares for Valentino and Orion, and Férnan Emeterio, and he meets Valentino and Orion at the pawn shop. Mateo Tellez Jr. is the other protagonist of They Both Die at the End, and he meets Valentino and Orion at Times Square, where they go to have their first date. Both boys receive a chapter from their perspective, in which they feel encouraged to live based on their or their parents’ interactions with Valentino and Orion.