Kobuntei is a three-storey wooden villa sitting at the heart of Kairakuen garden. It was built in 1842 by Tokugawa Nariaki as a study and resting place, and restored to its original appearance in 2003 after being damaged by fire. The interior has traditional tatami rooms and sliding screens, and the upper floor has particularly fine views over the plum groves and Lake Senba.
Kobuntei is usually included in the Kairakuen admission fee during the Plum Festival. The rooms have information panels about the Mito Tokugawa domain and its cultural traditions, including the school of Neo-Confucian scholarship (Mito-gaku) that Nariaki patronised. Worth a visit on its own terms even if your Japanese reading is limited.