Nito-ryu (二刀流)
The term "nito-ryu" (two-sword fencing) is a general term for the technique of offense and defense with Japanese swords or other swords in both hands (left and right hands). This is also known as "nitoken-ho" (literally, "two-sword method"). Other meanings, such as working on an issue with two different approaches or doing two things simultaneously, are also derived from handling a weapon in each hand.
Japan
The major style of two-sword fencing in the Japanese martial arts is holding a honzashi (a long sword) in the right hand and a wakizashi (a short sword) in the left hand. Using a Japanese sword in each hand is hard because a Japanese sword is basically designed to be used by grasping with both hands and the fencer has to use both hands separately, and consequently just a small number of schools focus on two-sword fencing. Some fencers in kendo (Japanese art of fencing), which originated in Japanese sword art, use two-sword fencing as well. Fencers sometimes practiced using two swords at first until they became used to it and then returned to using one sword in order to master the one-sword martial arts.
The technique of two-sword fencing has been inherited by many classical Japanese martial arts in various styles, for example using an uchigatana (a type of sword used since the latter Muromachi period) in the left hand or holding a sword with a reverse grip, as well as some curious styles such as two-wakizashi fencing called nito-kodachi jutsu (literally, "two small-sword fencing," adopted by the Yagyu Shingan-ryu school, the Tendo-ryu school and others), nicho-jutte (two short metal truncheons), and nicho-gama (two-sickles). In the shuriken (a small throwing blade) art, they have a technique to keep a sword in one hand and throw shuriken with the other hand. Niten Ichi-ryu, the school established by Musashi MIYAMOTO, is the most famous among the Japanese sword art schools that emphasize two-sword fencing in Japan.
Also, Yoshisada NITTA is a well known historical two-sword fencing expert, and the 'Taiheiki' (the Chronicle of Great Peace) describes a scene in which he continuously flicks away arrows with a sword in each hand.
In the Okinawan kobudo (Okinawan classical martial arts) which arose in Okinawa and was greatly affected by China and Southeast Asian countries, a fighter holds a weapon such as a sai (an iron truncheon) or a tonfa in each hand.
Other countries
There were some short swords for the left hand, such as main-gauche, in Europe. Two-sword fencing has been more popular in China and Southeast Asia than in Japan, for example soken (fencing with two double-edged straight swords) and soto (fencing with two butterfly swords) in China, and Silat, Eskrima and Krabi-krabong in Southeast Asia (in Southeast Asia and China there are many different styles of two-sword fencing such as two short clubs, two daggers, and one long sword and one short sword).
The term 'nicho-kenju' (literally, "two pistols") is refers to holding and firing two pistols at the same time in western films.
Two-sword fencing in sports
Kendo fencers can use the two-sword fencing style in regular matches. However, senior high school and younger students are not allowed to use it. The All Japan Students Kendo Federation allowed university and college students to use it in 1992. Its basic style in a match is to parry an opponent's attack with a kodachi (a short sword) and attack the opponent with a tachi (a long sword). The kodachi is principally used for defense and putting an opponent off balance, and any kodachi strokes and thrusts generally cannot be a telling blow. Strictly speaking, a complete form stroke or thrust can be a telling blow even if it is made with a kodachi, but fencers can hardly make a complete form stroke or thrust with a kodachi because its ideal distance to an opponent is shorter, and also the strokes and thrusts made by a kodachi are judged more strictly than the strokes and thrusts by a tachi. This is why people generally do not think any kodachi strokes and thrusts can be a telling blow. In addition, a shinai (a bamboo sword) used as a tachi for two-sword fencing is somewhat shorter than an ordinary shinai.
In Sports Chanbara (a free-style Japanese combat sport based on sword fighting), players must be in the two-sword style in nito (two swords) tournaments, and players are allowed to fight in the two-sword style in ishu (a match between different weapons) tournaments.
During the Renaissance in Italy, one of the fencing techniques was to use a rapier in a dominant hand and a main-gauche in the other hand, but the main-gauche was used only for defense, being handled like a shield.
A switch-hitter is sometimes called nito-ryu in professional baseball. In addition, a pitcher who can also play as a fielder is called nito-ryu. Players who have two completely different pitching forms were sometimes referred to as nito-ryu, written 二投流 (meaning "two pitching styles") instead of 二刀流.
Other nito-ryu
This is sometimes used as slang or jargon for a bisexual person (in most cases a male). This is also called ryoto zukai (which literally means "two-sword handler").
This term represents a person who loves both alcohol and sweets. This is because many people who love sweets do not drink alcohol very much and many people who love drinking alcohol do not like sweets very much.