K-system sample game and Cross Rook Technique

Today I played K-system in Double Swinging Rook.
The kifu is shown below.
Actually I failed in opening, but defended and won the game.

In figure. 1, can you find a Technique move?

figure.1

The answe is P-8d. The reason is that after P-8d, the game proceeded Px8d, Rx8d and resulted in Cross Rook aiming both the oppoenent's king and Bishop on 4d (figure. 2).

Cross Rook Technique appears occasionally and this is important technique.

After this, I succeeded in winning soon afterward.

figure. 2