While he was in prison after he lost the battle in Goryokaku, he wrote to his brother to teach him in detail how to make an incubator, soap and so on, the new way to raise silkworms and how to extract indigo, for the purpose of helping his brother's living.
五稜郭で敗れて、獄中にいる時、兄の家計を助けようとして手紙で、孵卵器や石鹸などの作り方や、新式の養蚕法・藍の採り方等詳細に知らせている。