Blind marathon is a sport where visually impaired people can run with sighted guides in pairs. In this paper, we present an assistant system for blind marathon runners called "Synchronized Running" that improves the guidance experience for the runners. Our proposed system allows both runners to match their running tempo and synchronize with each other, similar to a three-legged race case, without any direct physical attachment. Two modules are located on the ankle of both runners, that measure the acceleration of the visually impaired runner, and provide haptic feedback to the guide's ankle according the tempo of the running pace. This synchronization allows the guide to grasp a comfortable running pace towards the visually impaired person, allowing seamless running communication between both runners. The evaluation results indicate that our system encourage runners (primarily novice guides) to achieve comfortable guidance running experience toward the blind runners.