Miyoshi was born in 1861 in the village of Iwamura, now part of modern-day Ena.

A graduate of the Imperial University of Tokyo in 1889, he continued his scientific training at the University of Leipzig under the direction of German botanist Wilhelm Friedrich Philipp Pfeffer.

In 1895, he earned his Doctorate of Science degree and returned to Japan as Professor of Botany at the University of Tokyo.

Throughout his academic career, he studied the genera Prunus and Iris.

At the beginning of 20th century, he promoted the idea of ‘natural monuments’ for preservation, a concept he brought back with him from his period of study in Germany.