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faithful; devoted; loyal; honest; true
「忠実」 has another reading with different meanings.
原作に忠実な映画化が話題を呼んでいる。
A film adaptation faithful to the original is generating buzz.
彼は忠実な部下として上司を支え続けた。
He continued to support his boss as a loyal subordinate.
契約内容に忠実であることが信頼につながる。
Being faithful to the contract leads to trust.