いっ 相伝 そうでん
isshisōden

Noun

1. transmission of the secrets of an art, craft, trade or learning from father to only one child

Yojijukugo
いっ 相伝 そうでん わざ うわりには、彼 かれ りは たいした ことはないね。
isshisōdenno wazato iu wariniwa kareno keriwa taishita kotowa naine.
For a guy who was chosen by his father as the only son to be taught the secrets of this martial art, he doesn't have that much of a kick.