According to the tradition of the people (Joden OTSUKI and Yukichi Fukuzawa) who knew Seikei in life, he was too sensitive and tended to think melancholily.
成卿の生前を知る人々（大槻如電、福澤諭吉）の伝承によると、彼は神経が鋭敏に過ぎ、ふさぎ込んで考えこむ癖があったという。