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suddenly; casually; accidentally; incidentally; unexpectedly; unintentionally
不図、昔のことを思い出した。
Suddenly, I remembered the old days.
不図、見知らぬ人に声をかけられた。
Suddenly, a stranger spoke to me.
不図、彼の言葉が頭に浮かんだ。
Suddenly, his words came to mind.