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working adult; full-fledged member of society
来年から社会人になる。
I'll become a working adult next year.
社会人になって自由な時間が減った。
After becoming a working adult, my free time decreased.
社会人としてのマナーを身につけることは大切だと思う。
I think it's important to learn proper etiquette as a working adult.