[2] As there were no weight classes in the world championships until 1965, Natsui was the only champion in 1956.

[2] The International Judo Federation (IJF) was founded in 1951, and five years later IJF organized the first World Judo Championships, held in Tokyo on 5 March 1956.

[1] In the first round Natsui took only 3 seconds to eliminate the contestant from Cambodia, with the shoulder throw seoi nage.

[3] The match against Woodrey from Belgium in round 3 lasted 44 seconds, with victory going to Natsui.

[3] In the semi-final he met Henri Courtine from France; this match lasted only 8 seconds, with a tai otoshi win to Natsui.