A world made entirely of the things you forgot exists somewhere you can't reach. The movie knows this breaks something in you the moment you recognize your own lost treasures on screen. It's a feature-length love letter to childhood rendered in animation so alive it makes the forgetting hurt.
Haruka discovers that her cherished childhood teddy bear has vanished. Unlike most forgotten items, this one matters enough to chase. Following a mysterious trail, she slips into Oblivion Island: a dimension where forgotten treasures accumulate into an entire civilization built by creatures who collect what humans leave behind. These beings aren't malicious scavengers but archivists of nostalgia, preserving the objects people abandon as they grow older and move forward. Haruka navigates this strange world to reclaim her bear, but the journey becomes less about retrieval and more about confronting what it means to let go. She encounters the island's inhabitants, learns why they hoard these discarded memories, and questions whether some things deserve to be forgotten while others demand to be held onto. The film moves between whimsical and melancholic, presenting childhood memories as both sacred relics and weights we eventually shed. It's a meditation on growing up wrapped in adventure, asking whether leaving things behind is betrayal or necessity.