In shogi, Central Rook (中飛車 nakabisha) is a special class of Ranging Rook (振り飛車) openings (戦法) in which the rook (飛) is positioned on the fifth (central) file. It is also possible to castle your king on the left after playing central rook.
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Traditional Central Rook
The standard way to play Central Rook is for the player to close their bishop (角) diagonal with a pawn (歩) advanced to the 6f square when played by Black (先手) or advanced to 4d when played by White (後手). This is sometimes called ノーマル中飛車 nōmaru nakabisha "Normal Central Rook" which contrasts with a Central Rook position that allows a bishop exchange to occur at anytime, such as Cheerful Central Rook.
Games that have the bishop diagonal closed are known as slow games.
Ranging Rook strategies like Central are also traditionally played by White against Black's Static Rook (居飛車) position.
The Central Rook player will commonly use either a Mino (美濃囲い) or Anaguma (穴熊) castle. Since the rook is positioned on the fifth file, it prevents the player from making the usual Mino castle. Therefore, Central Rook's castle is often an Incomplete Mino (片美濃).
White's Central Rook
The opening starts by the usual four-move sequence that characterizes Static Rook vs Ranging Rook (居飛車対振り飛車) games as shown in the board position on the right. (See: Traditional Ranging Rook.)
3. S-4h. Black advances their right silver up and toward the center of the board. (This is a more flexible move than 3. S-3h.)
3. ... S-4b. White likewise moves their silver up and to toward the center. This move gives White the possibility of further moving the silver up to 6d through 5c (after a pawn push) as well to 4c or 3c. This left silver will likely be a main component of White's counterattack.
Although White also has the choice of moving their rook for this move (3. ... R-5b), moving their silver first instead keeps White's strategy more uncertain as well as giving White the option of playing a Double Yagura position (which is a Static Rook opening). This move, however, does delay ranging the rook to any other Ranging Rook positions on the fourth, third, and second files.
4. P-5f. This prepares for various Static Rook strategies.
4. ... P-5d.
5. G4i-5h. Black begins their castle formation by moving their right gold to the center file. Following this move, Black can start moving their king into castle.
The usual fortification is initially a Boat castle. Since the Boat castle is fairly weak castle, Black can later transition the Boat into stronger castles (such as an Anaguma or Left Mino, among others).
5. ... R-5b. This move signals White's Central Rook strategy. Since the rook has moved to the center, White can now start their castle development.
6. K-6h K-6b, 7. K-7h K-7b. After seeing White's rook movement, Black usually starts moving their king away from their rook and toward the king's castle position. White likewise mirrors Black's king movements.
8. P-9f P-9d. Black advances their ninth file edge pawn to give the king more flexibility for escape in the end game. With this move, Black's Boat castle is complete. White responds likewise opening an escape hatch for their king with an edge pawn push.
Around this point, Black has a choice between attacking White on the right side of the board or attacking White closer to the center files.
In the first choice, since Black is fighting from the side, White can respond by building a Mino castle since Mino castles are quick to form and provide a good defense from the side attacks. This is shown in the immediately following subsection.
For Black's central attack, White may choose to build an Anaguma castle since this type of castle is stronger for defending against attacks from above compared with a Mino castle as shown in the subsequent subsection.
White's Mino vs Black's right side attack
9. P-3f.
9. ... S-4c.
10. P-2e B-3c.
11. S-6h.
11. ... K-8b. White continues castling their king to the eighth file. In this position, White can construct a Mino castle. However, it is also possible to move the king further to the 9a corner in order to build an Anaguma.
Transpositions
The sequence of moves shown above can also be flexibly transposed to different orders. Below are some other possible move sequences leading to the same position.
Silver Horns formation
A Central Rook Silver Horns (ツノ銀中飛車 tsuno gin nakabisha) structure is also possible. This strategy uses a Kimura Mino (木村美濃) castle.
White's Anaguma vs Black's central attack
7. S-5g. If Black is attempting a central attack, they will start advancing their right silver upward on the fifth file.
Cheerful Central Rook
Another variant of Central Rook called Cheerful Central Rook (ゴキゲン中飛車 gokigen nakabisha) keeps the bishop diagonal open. This is a more aggressive strategy since the bishops may be exchanged at any time during the opening.
vs Side Pawn Capture variation
There is an older joseki for a Central Rook position by White played against a Static Rook position played by Black that captures White's side pawn on 3d. (Cf. the Double Static Rook Side Pawn Capture opening.) It was seen up until the 1950s, but is now unpopular with professional players as the situation appears to strongly favor Black. An example of this opening occurred in the meijin match between Masao Tsukada (塚田正夫) and Yoshio Kimura (木村義雄) on June 6, 1947.
The opening starts with a position that looks similar to White's Cheerful Central Rook (which hadn't been invented yet). However, after the fifth move, instead of swinging the rook to the central file as in Cheerful Central Rook, White advances their central pawn to the middle rank. This allows Black to trade pawns on the second file.
Subsequently, Black captures White's side pawn while White swings their rook to the central file.
After moving their rook back to the second file, White attacks on the central file and then trades bishops.