In this article, we will outline the co-design process of the Future Story Chasers storytelling game methodology. Future Story Chasers is a research project aimed at fostering the collective creation of stories based on a common fictional premise. A first experience was carried out in late 2017 in three primary and secondary schools in Barcelona, with approximately 200 participants from three different age groups and diverse social backgrounds. Previously, a co-design process was carried out to establish the grounds for the narrative and game experience, with a twofolded aim: to nurture adaptive storytelling strategies through a broadly defined fictional universe set in a near future; and to stimulate reflection around social issues, meaningful for the participants, through fiction and creativity. We will focus on the design process of the board game that served as the starting point for the experience and the challenges for the overall research methodology.