Etymology and distribution of 關本.

Sekimoto 【關本】^{レベル2
About 30}  The Japanese surnames etymology dictionary.

Niigata-ken Shibata-shi , Ibaraki-ken , Saitama-ken . Distribution including Tsuyu too. A variant of 津久井 . Yamagata-ken Yamagata-shi Kasagi-machi was in the Edo period in the clan of the Yamagata of the Clan office. 津久井 Tsukui reference.