Well the structure of the tournament just had Semifinals then Final. So The Top4 don't seem to play one another in the tournament like the City tournaments.
For the whole of Japan? I know for tournaments only 15 Players are allowed in a Squad for tournaments.
Likely squad of 15:
Eiji Sawakita, Masashi Kawata, Fukatsu Kazunari, Minoru Matsumoto (Sannoh), Moroboshi Dai (Aiwa),
Rukawa Kaede, Akagi Takenori (Shohoku), Maki Shinichi, Jin Soichiro, Nobunaga Kiyota (Kainan), Tsuchiya Jun (Daiei), Morishige Hiroshi (Meihou).
Not sure who else to add to make 15.