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to hold fast; to protect to the end
最後まで秘密を守り抜いた。
I kept the secret to the very end
彼は城を守り抜く覚悟だった。
He was determined to defend the castle
彼は困難な状況でも自分の信念を守り抜いている。
He continues to hold fast to his beliefs even in difficult situations.