Some memories are worth erasing. Others erase the future.Seventeen-year-old Ione erases a painful memory expecting relief. What she does not expect is proof that forgetting is never private. In Lumen Harbor, memories are currency. They are traded to ease grief, erase regret, and survive what life takes away. The system is regulated, trusted, and designed to make forgetting feel harmless. Until Ione discovers that her lost memory did not disappear. It was transferred. As memories begin vanishing across the city, Ione uncovers a hidden economy built on quiet theft and shared loss. Every erased moment leaves someone else carrying the weight, and a catastrophe buried years ago starts to surface. Stopping the damage means remembering what the system was built to erase. But choosing to remember may cost more than forgetting ever did. The Day Tomorrow Forgot Us is a gripping YA speculative science fiction novel about memory, identity, and the unseen harm of systems that promise relief without consequence.