- Sumo is a Japanese national sport. It is a battle of 2 persons in the ring and its goal is to reverse the adversary or push him out of the ring. Being played since Nara-Yamato period, professional wrestlers appeared in Muromachi period and sumo for religious charities had been very poplar during Edo period.
- In old times, sumo matches, called "Kanjinzumo" took place on the ground of shrines or temples in order to collect the funds of their construction or reparation.
- Gyoji is a sumo referee. His role consists in opposing 2 wrestlers in sumo ring and directing the referee's fan to the winner after a match. If there is no protestation coming from ringside judges, he confirms the judgment by declaring the winner's name. The main houses of sumo referees are Kimura and Shikimori.
- Dohyo is a place where a sumo match occurs. Officially it has a circular form with 455 cm of diameter.
- The role of the ringside judges consists in watching a match, sitting at each side of the ring, in order to correct an eventual misjudgment of the referee. Elected among retired sumo wrestlers, they are now called Shinpan iin.