FANVERSE: Exploring and Extending Branching Story Universes Across Canon and Fan Fiction

Fan-written works and their shared canonical source collectively form a story universe of alternative narrative branches, yet existing platforms present them as separate linear stories, leaving readers to mentally reconstruct this universe across works. We thus introduce FanVerse, an AI-powered interactive system that transforms these works into an explicit branching story universe for integrated reading and authoring. FanVerse organizes each branch into branch-time states linked to supporting passages and aligns branches through shared events and divergence relations. Readers can move across branches to examine how narrative changes propagate through characters, relationships, knowledge, and events, and create a grounded new branch from any selected state. Technical evaluations show that the FanVerse pipeline supports reliable story universe construction, improved cross-branch reasoning, and more consistent branch extension. An exploratory case study further suggests that connecting interpretation with creation supports fandom sensemaking, with implications for designing fan-work engagement experiences that give users greater agency to navigate and shape story universes.