You're right, there's a rather large bug in the Geography system that you just brought to my attention - the locales within the Tinto Republic, being a separate country (as it seceded after Suikoden II), are actually somewhat hidden right now.
Strangely, the Tinto Republic nation page (accessible from the 'Other Locations' page) does not link the the locales within it. However, they are linked to here -
http://www.suikosource.com/history/geog ... ale_id=182
Tigermouth is the exception - its actually just in the Dunan guide, as its on the Two River side of the mountains.
Tigermouth
Population: 1000
A small village that is built at the foot of the Lamp Dragon Mountains. It is known as having a very mild climate, making it an ideal place for summer retreats.
Blue Moon's comment:
An unlikely place for the oft unseen alternate ending. Also known as the "place Shu gets violent."
I don't know any special facts about any of the three villages involved, past what happens in them during Suikoden II.