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落ち込む， 落込む， 落ちこむ， おちこむ
1. to feel down, to feel sad, to be depressed, to be in low spirits
2. to be in a slump (business, economy, etc.), to be in an unfavourable condition
3. to fall into (e.g. a hole)
tbd
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
