Tips No. 23-2 : Learn cases for check mate by "tsume-shogi"!

The answer is dropping B x 3a - K x 1b, dropping P x 1c! N x 1c, dropping G x 2b checkmate.
That move is for checkmate by five moves as diagram #2.

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Please look at the diagram #3. There are many pieces, It would be difficult to understand. But it is a same with diargam #2.
Please try to chase steadily it in your head.

"tsume-shogi" is a best way to learn checkmate of varied situations and deverop your foresight.