On January 7, 1870, Nishikubo was born in Hachinohe, Nabeshima Village, Saga County, Hizen Province; in 1874 he moved to Tokyo with his father, and in August 1875, entered Tomoe First Elementary School in Tomoe-cho, Shiba Word, Tokyo (later the school was changed its name to Tomoe Elementary School, and belonged to Minato Word, and closed in March 1991).
明治2年12月6日に肥前国佐賀郡鍋島村八戸に生まれた西久保は明治7年父に従い東京へ移住、明治8年8月から東京芝区巴町の第一番小学鞆絵学校（後の港区立鞆絵小学校。平成3年3月閉校）に入校する。