Let’s look at the chess board where bastard principal interferes with Ayanakoji’s move:

The situation is Sakayanagi’s Black is “threatening” 1. … Qxg2 check “Threatening” in quotes because as we see in the story, the obvious defensive White is move 1. gxf3 ?

The question mark because it’s a poor move because moving the Pawn out of the way allows:

2. … R-g6 ch

and maybe

2a. Q-g5 Rxg5 ch But this extra move just delays the inevitable

3. K-h1 Bxf3 mate

Let’s talk about Ayanakoji’s intended move after the original setup:

1. Q-g5 by threatening checkmate 2. Qxg7, Ayanakoji sets up an exchange of Queens, and maybe other pieces.

Any reasonable scenario after that results with his White having a significant material advantage.

If Black responds with

1. … Qxg2 ch then

2. QxQ BxQ

3. KxB …

And the end game starts with White having 2 Rooks and a Bishop, which should easily overwhelm Black’s one Rook for a White victory.

If Black takes White’s Queen with the pawn

1. … Pxg5 then Black’s Queen is also lost

2. Pxf3

and we’re left with…

The doubled black Pawn on the g column blocks Black’s Rook from moving to g6 check, and also therefore prevents starting the checkmate process in the first scenario.

White has a significant material advantage with 2 Rooks, and a Bishop against Blacks 1 Rook and 1 Bishop.

Basically, even at the beginning of this scene Sakayanagi’s Black was already in a losing state being down 1 Rook, so any scenario with an even trade of pieces was to Ayanakoji’s advantage.

The only way for Black to win was for White to make a huge mistake which bastard principal provided for her.

p.s. Thanks to chess.com for providing a web-editable chess board.