Nuidoishiyama rises above Fukuura, giving Sai a proper mountain walk rather than just a coastal viewpoint. The climb is the local hike to do if the weather is stable: forest, exposed ridges, and broad views back over the village, sea, and folded Shimokita hills.
This is bear country, not a landscaped city trail. Carry water, wear real shoes, and use the bear bells provided at the trailhead if they are available. The reward is a sense of Sai's geography in one sweep: sea in front, forest behind, and almost no urban clutter between them.