noun
lost sheep
Literary or classical term for a sheep that has gone astray; often used metaphorically for a person who has strayed from the right path. Rare in everyday conversation.
「亡羊の嘆」という故事成語がある。
There is a classical idiom 'lament over the lost sheep'.
彼は若い頃の放蕩を振り返り、亡羊の思いに駆られた。
Looking back on his youthful dissipation, he was seized by the feeling of a lost sheep.