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transmission of the secrets of an art, craft, trade or learning from father to only one child
この技法は一子相伝で受け継がれてきた。
This technique has been handed down from father to son.
一子相伝の秘術を守り続けている。
They continue to guard the secret art passed down through generations.
一子相伝の家業を継ぐ決意をした。
I resolved to succeed the family trade passed down through generations.