[This got quite long! The Japanese Wikipedia page goes into unbelievable detail.]

Nikaido Tokuyo was born in 1880 in a mountain village in Miyagi. She finished her schooling at fifteen and became an elementary school teacher’s aide in the same year, like many rural girls; her students enjoyed their bouncy young teacher. Deciding to get formal education credentials, she applied first to the Miyagi Normal School, which no longer had a women’s department, and then to the Fukushima Normal School, which told her she had to be a resident of Fukushima; nothing daunted, she got herself adopted (on paper) by the editor of a Fukushima newspaper, started school, and graduated in 1899. At the Normal School she found the old-fashioned gym classes boring, but did well in them as a student teacher, allowed to wear her “sports” outfit (tight sleeves and a hakama) on a daily basis.

Teaching once again, she encountered Naganuma Chieko, the older sister of one of her students; they became lifelong friends. In 1900 she took leave and entered the Women’s Higher Normal School in Tokyo, where she studied pedagogy with Yasui Tetsu as well as gym and poetry. She graduated in 1904 and went to teach at the Ishikawa Girls’ Higher School, where—having expected to teach Japanese—she found herself assigned to gym classes; resentful at first, she found they improved her own health as well as her students’, and began taking gymnastics lessons with Frances Kate Morgan, a local Canadian missionary. Eventually she progressed to coaching local elementary school teachers in gymnastics instruction. A gymnastics demonstration at which students danced the quadrille, with a live band sponsored by the prefectural governor (whose daughter was among the students) was so popular that local high school boys, unable to get tickets, climbed over the fence and caused a minor riot.

Tokuyo was transferred to Kochi in 1907; there she became famous for reading Shakespeare to her students while they rested in the shade between exercises. In 1911 she took up a position at the Women’s Higher Normal School, where she briefly worked with Inokuchi Akuri; the following year, the Ministry of Education sent her to England to study gymnastics. There, under Martina Bergman-Österberg, she was able to study systematically in comparison to the bits-and-pieces, mix-and-match approach she had followed so far (her instructors were surprised at how little she knew about standard gymnastics).

After her return to Japan in 1915, she taught dance, gymnastics, games, and sports (including cricket, the fruit of her study in England) at the Higher Normal School as well as Tokyo Women’s University, publishing several books as well. After some clashes with her colleagues, she resolved to set up her own school. In 1919 she formed the Association of Women Gymnastics Teachers; in 1922 she founded the Nikaido Gymnastics School to research women’s physical education and train women teachers; it was her stance that women should educate women. In addition to Tokuyo herself, instructors included various military doctors and athletes as well as her little brothers, who showed up to teach Japanese, while her mother Kin—once a tough farm girl who hated sewing—ran the dormitory. In 1925, stimulated by the matriculation of the Olympic runner Hitomi Kinue, Tokuyo decided that her school needed to train athletes as well as teachers. The school was approved as the Japan Women’s Vocational School of Physical Education in 1926.

In her later years Tokuyo became increasingly nationalist as Japan slid toward wartime status; she had a perpetual adoration for the military. She died in 1941 at the age of sixty. (In 1943, a newspaper printed her thoughts on the establishment of a women’s physical education exam; the text actually came from her brother, but she was considered better news regardless of the fact that she had already been dead for two years.) Among her students were the dance teacher Tokura Haru, who was instrumental in keeping the school solvent, and the politician Yamashita Harue; Tokuyo’s school remains in existence as the Japan Women’s College of Physical Education. She was said to have had the powerful voice of an opera singer, or rather of the gym teacher she was; she also had a repertoire of insults to rival Captain Haddock, including “jelly on horseback!” “rotten washcloth!” “misshapen rock candy!” and so on.

Sources
https://www.jwcpe.ac.jp/college_info/idea/founder/ (Japanese) Includes a picture of Tokuyo with her students in uniform