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sharp sword
快刀で乱麻を断つような解決策だった。
It was a solution like cutting through a tangled mess.
快刀を振るって敵陣を突破した。
He broke through the enemy lines wielding a sharp sword.
名工の作った快刀は切れ味が鋭い。
A sharp sword made by a master craftsman has a keen edge.