In 1858, he was restored to the post of "rōjū" by the "Tairō" Ii Naosuke, and quickly was seen as Ii's right-hand man, taking a leading role in difficult situations, such as the Ansei Purge, the ratification of the Ansei Treaties, and the opposition to Hitotsubashi Yoshinobu from becoming "shōgun". In particular, his heavy-handed approach to forcing Emperor Kōmei to accept the ratification of the Harris Treaty and his suppression of pro-"Sonnō jōi" samurai in Kyoto drew the wrath of Yoshida Shōin in particular, who made many inflammatory speeches and writings urging Manabe's assassination.