A marathon event held in spring at the shores of Lake Toya. The event features a variety of races, from the full marathon of 42.195 km to 10 km and 5 km courses, as well as a parent-child pair race. Participants can also opt for double entries. After the marathon, runners can wash away their sweat at the Toyako Onsen (hot springs), making it a popular event that attracts many runners from all over Japan and abroad.