Demon Killer.

Ranging rook, a surprise attack · none (the king never moves) · 鬼殺し onigoroshi

The idea

A famous 奇襲, a surprise opening, and the source is candid about it: there is a correct defence, and against a player who knows it the attack comes to nothing. That is also why it is worth knowing: a trap you have seen once is much harder to fall into.

Black jumps the knight to 7g on move three and on to 6e, against the proverb that a knight that jumps too high is food for a pawn. The bishops come off, Black drops a bishop in the middle of the board on 5e, and it attacks the silver on 2b and the pawn on 6d at once.

From there Black brings the rook to the seventh file and breaks through on 7c, where three of Black’s pieces bear on the square against two of White’s.

How it goes together

Both sides’ moves are shown, because this opening is an agreement rather than a system: one player cannot reach it alone, so a one-sided list of moves would be a fiction.

The plan once you are set up

• Know that it is a trap. The line only works if the defender walks into it; the source says plainly that against the correct defence it misses.
• As the defender, look at what the line punishes: White’s pawn push against the knight on 6e is the pawn the bishop drop on 5e then wins. The source does not give the correct defence itself.
• Count the attackers on the break square. The breakthrough on 7c works in this line because three of Black’s pieces bear on it and only two of White’s defend it.
• Play it for fun, not as a repertoire. A surprise opening is only a surprise once.

What to watch for

• The bishop drop on 5e. The whole trap turns on it: it attacks a silver and a pawn at once.
• Your own king, if you are Black: it never moves in this line, so if the attack fails the counter-attack finds it at home.
• The proverb 桂馬の高飛び歩の餌食. The source points out that this opening ignores it completely.

What it is played against

A defender who does not know it, which in practice means beginners. Black commits on the third move, so it is the player who opens who chooses it.

The New Demon Killer

New Demon Killer (新鬼殺し)

Yonenaga Kunio improved the Demon Killer for the case where White pushes the rook pawn on move two. Black heads for a Quick Ishida with the pawn to 7e, puts the bishop on 7g, covering 8f, and swings the rook to 7h. When White trades bishops, the knight recaptures on 7g, the square the old line jumps to on move three.

The board is ja.wikipedia’s base position after nine moves: 7f, 8d, 7e, 8e, the bishop to 7g, 3d, the rook to 7h, the bishop trade on 7g and the knight taking back.

In the old line White’s pawn to 6d stops the knight; with the bishops already off, Black has more play, and ja.wikipedia gives a prepared answer to each of White’s bishop drops, among them the pawn to 7d against a bishop on 8g, 7f or 4e. If White plays the silver to 6b before the trade, Black can go for the Quick Ishida with the pawn to 7d.

Yonenaga’s 1988 book on it ran to close to sixty printings, but professionals did not take it up: against quiet play, ja.wikipedia says, Black gets nothing from moving first.