Cognitive decline among older adults presents a growing public health concern, underscoring the need for accessible and engaging interventions. In this paper, we present WisdomTales, a mobile game designed to enhance cognitive abilities in older adults through arithmetic practice, interactive storytelling, and learning-by-teaching. The game integrates the concept of magic multiplication, a mental math technique that simplifies multiplication, into a visual format that presents arithmetic challenges in meaningful and relatable contexts. Users engage in narrative-driven activities alongside a virtual grandchild character, reinforcing mathematical concepts through dialogic learning powered by a teachable agent. We conducted a pilot study involving 30 participants to assess users’ satisfaction, engagement, and perceived cognitive stimulation. The results show that participants particularly appreciated the game’s accessibility, personalized design, and the opportunity to teach the virtual agent.