Ii Naosuke was a prominent Tairô of the Bakumatsu period, known for his support of ending the maritime restrictions of the Edo period and "opening" the country, and for his engineering of the Ansei Purges in which he purged from the government a great many shogunate officials belonging to rival factions.
Born at the Keyakigoten, the lord's private residence within Hikone castle, Naosuke became lord of Hikone han at the age of 36. He was named Tairô in 1858, and was a strong supporter of Hotta Masayoshi's having negotiated and agreed to the Treaty of Amity and Commerce (Harris Treaty).
Among his many activities as Tairô, in addition to the Ansei Purges, Naosuke suggested the succession of Tokugawa Iemochi to the position of shogun following the death of Tokugawa Iesada, and restored Manabe Akikatsu to the rôjû after disagreements with Mizuno Tadakuni forced Akikatsu to retire from the position.
- Plaques on-site at Hikone castle.