Tokunaga 【得永】4 The Japanese surnames etymology dictionary.
Kumamoto-ken . Terrain . From a swamp and a fence. Kumamoto - ken Tamana - shi In Yokohama town Yokohama told 1854 (first year of Ansei) renamed from Fujimoto surname. There is also a story that he was supervising the reclamation work in the Edo period in the same place. 藤本 reference.