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just (now, at the moment, etc.); just as; in the act of; as soon as; at the moment that
家を出た途端、雨が降ってきた。
The moment I left home, it started raining.
電話を切った途端に泣き出した。
She burst into tears the moment she hung up.
扉を開けた途端、猫が飛び出した。
The cat dashed out as soon as I opened the door.