Trails are places to pass through and their networks have developed as people and objects transport. They also have been places for interaction of people and cultures, traditional events, recreations and evacuation. In this paper, Minamisanriku Town, a coastal town in northeastern Miyagi Prefecture, was selected as the study area in which we investigated changes that have occurred throughout time in existing trails and in the relations between trails and people. We analyzed topographic maps, historical documents, and hearing surveys of residents and related organizations. The results showed that trails in Minamisanriku Town have traditionally been used for transport, trade, procurement of food and wood, and religious events, and that they have changed along with changes in people’s lives. Main routes have moved from trails in the mountains to coastal paved roadways, a move that increased the impact of tsunamis. Mountain trails have become ruined and are currently disappearing, but they work as emergency routes when a tsunami hits. The results showed that keeping mountain trails in good condition and preserving mountain trail networks is important not only for environmental education and for preserving traditions, but also to provide emergency evacuation and transportation routes during disasters.