## 1 Introduction
Regarding platform design, this research advocates for the utilization of virtual reality narrative and collaboration platforms, as they offer a dynamic and cooperative setting where users can inspire one another to collectively develop intricate and profound storylines. By amalgamating multiple users to collaborate and leverage their individual strengths, the resulting narrative is enriched and diversified. From the user's standpoint, engagement in co-creation and interaction not only facilitates the enjoyment of the creative process but also fosters emotional connections among users, thereby enhancing their comprehension of and dedication to the storyline. This dual involvement of emotion and cognition transforms users from passive spectators to active contributors in the creative endeavor, significantly augmenting their sense of dedication and involvement. Therefore, we have developed a Virtual Reality Card-based Interaction and Story Co-Creation Collaborative System named Co-relay. This system introduces a unique framework that combines a multi-player cooperation mechanism, interactive card system, and dynamic story progression. Co-Relay is designed for both two-player and four-player modes, allowing users to engage in collaborative storytelling by selecting character cards, customizing avatars, and uncovering the narrative's mystery through shared clue card collection and decision-making via social discussions. For instance, players can assume various roles in crafting a semi-open-ended crime mystery narrative, utilizing interactive decks to exchange information, integrating clue cards to deduce suspect motivations, and unveiling plot twists. The system incorporates a multi-ending design influenced by player choices and performance, maintaining narrative coherence through the assistance of Artificial Intelligence Generated Content (AIGC). This enhances replay value and emotional involvement, distinguishing it from conventional narrative collaboration platforms. By merging story co-creation with virtual reality environments and incorporating gamified interactions and AIGC compatibility, the system enhances story replayability and enables personalized branching. Emphasis was placed on ensuring sustained user engagement and personalization levels. After this, we performed user testing and experimental investigations to analyze interaction data and user experience by comparing Co-relay with website-based platforms for collaborative story writing. Our study makes the following contributions:  
1. We enhance the theory of interactive storytelling design by empirically verifying the influence of card-based interactive storytelling authoring design and virtual collaboration on user engagement. 2. We introduce Co-relay, a virtual reality (VR) narrative and collaboration platform for collaborative story creation that enhances user engagement and immersion, fosters creativity, and addresses emotional and social needs. 3. Our investigation explores the use of interactive story co-creation design framework and VR technologies to create immersive settings in multiplayer narrative encounters, elevating user-driven narratives for enhanced social interaction, educational applications, and therapeutic interventions.