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かつて， かって， 嘗て， 曾て， 曽て， 都て
1. once, before, formerly, ever, former, ex-
2. never yet, never before, first time, still not happened
曾经，以前，前-；从未如此，从未有过，首次；还没有发生过
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お互いに， おたがいに
1. mutually, with each other, reciprocally, together, both
相互, 彼此, 相互, 一起, 两个都
は
1. indicates sentence topic
2. indicates contrast with another option (stated or unstated)
3. adds emphasis
指示句子的主题；表示与另一选项（无论是否明确提及）形成对比；表示强调
