His health improved to such an extent that he became a leader of the school's karate club, and his friends dubbed him Chippaii Matsu, a nickname meaning "tenacious pine tree".

After graduation in March 1928, he began to study martial arts full-time, moving to Shuri and training under Taro Shimabuku (島袋善良)and Ankichi Arakaki.

Later that year, he was conscripted into the Japanese army in the 47th Infantry Regiment, and fought in China for the Jinan incident before receiving an honourable discharge in 1931.

During his time as a police officer, Nagamine received further instruction in karate from Chotoku Kyan and Motobu Choki, and achieved the title of Renshi in 1940.

Nagamine retired as a policeman in 1952, and in 1953 he returned to Naha City and set up his own dojo, which he named "Matsubayashi-Ryu Kodokan Karate and Ancient Martial Arts Studies".