Hagihara went to Cambridge University in England to study differential equations under the mathematician Henry Frederick Baker[2] and relativity alongside Paul Dirac under the astrophysicist Sir Arthur Stanley Eddington.

[1] He returned to Japan in 1925 but left for the United States three years later to study the topology of dynamical systems at Harvard University under George David Birkhoff on a Rockefeller Foundation Fellowship.

[2] In 1935, he published a paper showing that the trajectory of a test particle in the Schwarzschild metric can be expressed in terms of elliptic functions.

[3] In 1961 he was elected vice-president of the International Astronomical Union and president of the IAU's commission on celestial mechanics.

[2] He retired from all of his official duties, except for the Japan Academy, in 1967 and devoted himself to writing his comprehensive five volume work, Celestial Mechanics, which was based on his lecture notes.