In 1862, Tanetatsu was assigned to bugyo (Commissioner) of Bakufu Gakumonjo (National College managed directly by bakufu), although his status was still heyazumi (second sons and younger who were in their adolescence and has yet to be independent from the family headed by the eldest son).
文久2年（1862年）、部屋住みの身で幕府学問所奉行に登用される。