- Knight: in 1.0, right after Shinji returns to NERV after his brief escape, Fuyutsuki is learning to play shogi while chatting about how Shinji acted as expected, the piece he moves is the "knight".
The knight can only move forward, it can't turn back, it's always faced with a choice, going left or right, and it's unique being the only piece that can jump over the enemies.
"Eva is a story of repetition. It is a story where our protagonist faces the same situation many times over and determinedly picks himself back up again. It is a story of the will to move forward, even if only a little".
Shinji is always chosing between two option, stay or leave, fight or give up, save Rei or run away...
Shinji is unique as an impact trigger.
A knight usually have a princess to save, Asuka is called "princess" by Mari, and Shinji is urged to "save the princess".
- King: Gendo is called by Kaworu "king of Lilin". It's the piece that commands the other, he doesn't do much, he plans. Gendo plans a lot in the movies, he's the king of mankind in its battle against the angels.
In every game of shogi there are two kings but they are not equal, the "king general" is reserved to the reigning champion while the "joweled general" is given to the challenger.
In the first act of Q Misato is in charge of WILLE and the famous "you'll do nothing" scene it's an obvious callback to the reunion between Shinji and Gendo in 1.0 (and also Shinji and Gendo's reunion later in the movie). Misato is the "joweled general", Gendo is the "king general". WILLE is challenging NERV.
- 4 lances: every player can use two lances, so there are four lances in every game. Four are also the lances showed in 2.0.
[The article says something regarding the ability of the lance to stop the other player's movements like the lance of Cassius stopped N3I or the Longinus stopped Mark.06 but I'm not sure of how it works]
- 9 pawns: nine pawns are given to the two players, they can move only move one square forward and they are all equals.
Kaworu came out of the fifth coffin in a group of nine on the surface of the Moon. He gets on the scene in an epic way, but he's deceived and killed like a sacrifical piece for Gendo's plan.
Rei of course in another valid candidate. She's made in serie, she has no soul.
[I also noticed that she pilots Mark 09 in Q]
- Promotion: if a piece can make it to the furthest one-third of the board can be promoted and it's powered up. Misato and Kaji have an higher grade in the rebuilds compared to NGE.
- Capture: an enemy piece can be captured and used against the other player. In 2.0 Mari is fighting an angel captured by SEELE. This capture will be useful later as we are shown in Q the Nemesis Serie, something very similar to the angels (cores and rainbows too) controlled by SEELE.
- Drops: when a captured piece is used it's "a drop". In 2.0 basically every new character is dropped. Asuka comes from the sky inside Eva 02, Mari is litteraly dropped over Shinji with a parachute, Sahaquiel fall from orbit, Eva 03 is moved by air and Kaworu too came from the Moon.
- Repetition: [I'll quote Wikipedia here] "If the same game position occurs four times with the same player to move, either player loses if his or her moves during the repetition (sennichite) are all checks (perpetual check), otherwise the game is considered a draw. However, in Shogi a draw is not counted for. Players have to restart their game(s) until a winner is declared".
The number four it's a constant in the rebuilds. If an impact will happen in Shin Eva it will be the fourth, called Final impact in the preview, and it will cause the end of everything.
[INSERT PREFERRED LOOP THEORY HERE]
Fuyutsuki v Shinji
- Shinji is a newbie compared to Fuyutsuki, he barely knows the rules. He knows them as much as he knows the world he lives in after the 14 years sleep.
- The game was rigged from the start: Fuyutsuki tells Shinji he will not use the gold general, the rook and the bishop. Usually the experienced player doesn't use the rook, the bishop and the lances. The lances will be crucial to Gendo's plan later in the movie, that's why he keeps them.
- Fuyutsuki moves a piece than declares that Shinji will lose in 31 moves. 31 minutes later Kaworu dies.
- The match is resetted.
- Fuyutsuki pile up the pieces in the middle of the board and they start picking up their army one piece at the time.
- Shinji picks a promoted pawn. Fuyutsuki gives the photo to Shinji.
- Fuyutsuki picks a promoted knight and tells Shinji about Yui's death. Shinji is the knight, but at this point he could be a "promoted knight". [The article here links another theory on Shinji's nature. Basically after the Zeruel incident he may no longer be a mere human but something more]
- Shinji picks a pawn and the pile crumbles. Everything that Shinji believed to know was destroyed.
It's important to notice that the first piece Shinji picked was a promoted pawn while the second piece was a simple pawn. It could be reference to Kaworu being declassed from first to thirteenth angel or Shinji's feeling for Rei: she was unique, now she's just one of many clones.
- Fuyutsuki picks the king, Gendo, then he picks all the missing pieces.
- Shinji resign. He's crushed both on the board and psychologically. In the last shot of the board we see Fuyutsuki's pieces all set up and Shinji's pieces casually scattered.
Source: (1) (2)
The articles are easily readable if translated in english by Google translate (I tried and to me it seemed okay).
I used the search function and all I've found about the Shogi was this vague post dating January 2013.