The house is designed for a retired couple, with an adjoining guesthouse to accommodate visits from their children and grandchildren. Together, the two volumes form a domestic setting that balances everyday living with moments of gathering. The site is defined by a clear natural condition. A pristine river, part of the headwaters of the Tone River, runs along one edge, while a dense forest occupies the opposite side. The house is arranged as a long, linear volume that traces this boundary, positioning itself between water and woodland. This elongated proportion shapes the spatial experience of the interior. Moving through the house becomes akin to walking along the river within the forest, with shifting views unfolding along its length. Openings are oriented to both sides, facing the river to the south and the forest to the north, allowing the building to mediate between these two environments. Rather than treating the site as a single orientation, the design weaves together these contrasting conditions, establishing the house itself as a threshold. It becomes a continuous inhabitable edge, where landscape, movement, and dwelling are brought into alignment.