Start in Yoichi. Follow National Route 5 to the south. For the next 10 km the street follows the valley. Then there is a medium accend and a ca. 1 km long tunnel to a small pass (226 m). After the descend follow Route 276. After ca. 2 km turn right to Hokkaido Route 269 to Shakotan. Directly behind you is Yotei-zan. After 8 km you hit the sea shore and National Route 229. From here on the street follows the sea shore. After 40 km and many tunnels (there are more than 40 of them on the whole trip), you see a light house, a turn to the left after a short accend leads you there. After 15 more kms, Route 229 makes a turn to the right. You can continue along the sea shore aon Hokkaido Route 913. The route goes a little bit inlands and meets National Route 229 on a hilltop (150 m). After the descend you are in Bikuni, a famous place for fresh sushi. The street continues along the seashore and shortly before Yoichi is a small hill to climb.
This clockwise circumvention of Shakotan always has the seashore on your side of the street. The color of the water change from time to time and there are many beautiful rock formations along the coast. In the tunnels, I took my front light, pointing backwards, into my right hand. Thus car and truck drivers were very careful when overtaking.