Z (absolutely unmatable position, by nyanko)

"Z" is very important concept in shogi.
Z means absolutely unmatable position no matter how many pieces the opponent has in hand.
(The name "Z" derives from Japanese "Zettai Tsumanai", which means absolutely unmatable in English.)
For example, the sente king in figure. 1 is in Z. If gote will move G*2h, sente will Sx2h, and +Nx2h is not check. Also, if gote will move B*3i, sente will Sx3i, that position doesn't mate.
When you castle king in Silver Crown, the position like figure. 1 sometimes occur. So in that case, you can apply the concept of Z.

  figure. 1

If your king is in Z, it becomes easy to judge whether you should attack or defense, furthermore you can focus entirly on thinking move of attack. Additionaly, when your king is in Z, there are many cases that you can win even if you won't the best move.

Figure. 2 is my game of 10 seconds shogi, the opponent is amatuer 5 dan.
In blitz game, Z is more effective because it becomes easy to read.
The last move in figure. 2 is P*4g.
What do you move in this position?

 Figure. 2

It's the technique that the Gold in 4h doesn't escape.
When the opponent will move Px4h+, my king in that position is still in Z.
Therefore I could focus entirly in attacking.
So I moved Bx3c+ in figure. 2.
After that, Gx3c, S*2c, B*1c, +Rx3c, Nx3c, N*3e, B*6g, G*5f, R*8b (figure. 3).

Figure. 3

In figure. 3 you can take the Bishop (Sx6g), but it's too pasive, as commonly said that speed is more important than material gain in Endgame.
I moved Sx1b+ and continued attack.

The following is the entire game. Probably my attack is not best way, but my king is Z so that I just had to maintain 2-move clearance of the opponent's king, it was easy to win.
As above, it's effective to keep your king Z and not permit the opponent's king Z.