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留守， 留主， るす
1. absence, being away from home
2. house-sitting, house-sitter
3. being left unattended to (of one's studies, etc.), neglecting
不在家，离家在外
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
