Before the tachi-ai, you get a close look at the psychological side of Sumo. The two rikishi who are participating in the bout enter the dohyō and face one another. The first ritual performed is the shiko. The rikishi move their feet to the edge of the tawara and turn their backs to the center of the dohyō. Here they squat, clap their hands, raise their right legs as high as they can, and stomp it back down to the floor. They will repeat this with their left legs as well.
The rikishi rise from the shiko and step outside the ring of tawara, squatting in their respective corners. Here, they are given the chikara-mizu (a ladle filled with water that is said to bring them strength). They use the chikara-mizu to rinse their mouths and are given the chikara-gami afterwards. The chikara-gami is a piece of paper with which they wipe their mouths.
During this time, the gyoji is announcing the names of the two competing rikishi. He does so in a special, high-pitched voice. Once the rikishi have finished their purification rituals, they return to the side of the dohyō from which they entered. Once more, they squat and face one another. They keep their knees wide in a position called sonkyo. They clap their hands and then raise their arms into a horizontal position. This is done to show that neither rikishi is hiding a weapon and that they wish to have a fair fight.
The rikishi rise once more and return to their corners. At this point, the kensho are presented. These are the banners that represent the prize money that sponsors have placed on that bout and that will go to the rikishi who wins the bout. Each banner represents a different sum of money and, as they are displayed, they are carried around the dohyō by the yobidashi. (Note: Kensho are only allowed for the Makuuchi division.)
Before the yobidashi have even exited the dohyō, the two rikishi take a handful of salt and throw it onto the dohyō as they re-enter it. The salt is meant to purify the dohyō upon which they will compete and to drive away any malevolent spirits that might be present.
The rikishi then move to the center of the dohyō and position themselves directly behind the shikiri-sen (starting lines) that are painted on the dohyō. Less then arms-length from one another, the rikishi engage in an intense stare down and perform the shiko once more.
The rikishi rise, take a pace or two backwards and squat again, keeping their backs straight. They rise and assume the shikiri position (knees spread, body leaning forward, and fists planted on the ground). The rikishi will repeat this entire process two more times. The rikishi make a great show during these rituals to intimidate one another and get the crowd going. The third time the rikishi face one another at the center of the dohyō, the tachi-ai is imminent.
At the tachi-ai, both rikishi must charge one another simultaneously; jumping up from their squat after touching both fists to the ground. The gyoji can restart the bout if he thinks that the tachi-ai was not simultaneous. In order to win a rikishi must do one of two things: either force his opponent out of the dohyō or force his opponent to touch the ground with anything other than the bottom of their feet.
There are, however, alternative ways that a bout can be won (or lost). A rikishi who employs the use of a kinjite (an illegal move) automatically loses the bout. A rikishi whose mawashi comes completely undone likewise suffers an automatic loss. A rikishi who does not show up for his assigned bout (due to injury or otherwise) also automatically loses the bout (this is called fusenpai).
Bouts in Sumo consist solely of one round and last (on average) about 6 seconds. On occasion though, bouts can last for up to several minutes. In bouts such as these, the gyoji or one of the shimpan (judges) may call for a mizu-iri (water break). The rikishi are carefully separated, are given a brief break, and are then returned to the exact position they left off in. It is the gyoji’s responsibility to reposition the rikishi after the mizu-iri. If, after another four minutes, they rikishi are still locked together, a second mizu-iri is called. The second mizu-iri makes the rikishi start from the tachi-ai once more. Further deadlocks such as this with no end in sight may cause the bout to end in a hikiwake (a draw). This result is extremely rare in modern Sumo as the last time a bout ended in hikiwake was in September of 1974.
Once the bout is complete, the gyoji must indicate the winner by pointing to that riksihi’s side of the dohyō with the gunbai (fan). The gyoji’s decision, however, is not the end all be all and could still be overturned by the shimpan who are seated around the dohyō. Should this be the case, the five shimpan meet in the center of the dohyō for a mono-ii. Once they have reached a consensus they can uphold the gyoji’s decision or call for a torinaoshi (rematch).
If there is to be no torinaoshi (or if the the torinaoshi is complete and a winner has been declared) the rikishi return to their starting positions and bow to one another. A gyoji who is not present on the dohyō, determines the kimarite (winning technique) used in the bout and it is then announced to the audience. The winner (if in the Makuuchi division) is then given the kensho. The dohyō is smoothed out and made ready for the next bout.