We present a design study developed in a kindergarten classroom to involve pupils in an initial exploration of direct proportional relationships within a storytelling activity. As a theoretical framework, we refer to different studies that support the use of storytelling to activate children’s interest and engage them in mathematical problem-solving activities. Following the theory of semiotic mediation, the problem-solving activity was designed and implemented to allow students to explore and use different artefacts, stimulating discussion, manipulation, and drawing. In particular, we opted for a measurement context that leads children to work with numbers and proportional relationships, following the study of the Russian psychologist Davydov. Finally, we will present some excerpts from the pathways to show how using discussions, manipulatives, and representations through specific artefacts allows children to strengthen their number sense in a first experience with proportional relationships.