Tsushima

Tsushima Mansion is a Neutral Fort located on an island North of Hirado Castle and Hakata. It is originally ruled by Lord So (who becomes your deputy after capture).

Upon capture, you will have the option to raze it (giving you Mon) or capture it. The capture option is the most useful as it gives you access to Tsushima Gunner's or deliveries of silk weekly and also gives you access to the companion Jungeun.