By hes foreign stay he does not receive anything from the enormous modifications of the Shotokan in the years 1939 to 1943.  Thus he has to learn many things after his return, whereby Miyata Minoru particularly helps him, there he was not accepted as equal one beside Egami, Nishyama and Obata.

He begins to inspire Karateka for the idea of the transformation of Karate into a match-sport.  Thus he wins also Nishiyama and Obata.  With them he creates 1949 the JKA (Japan Karate Association), which has the target to compile rules for Match-Karate and to spread Karate by instructor courses.

The JKA grows fast and spreads Karate by the instructors over the whole world.

When Nakayama dies on April 15th 1987,  the JKA is missing at a successor and the splintering of the JKA begins.