Izumo (イズモ村 Izumo Village) is a small island continent that lies in the northern part of the Eastern Sea. Within the island of Izumo is a city of the same name. It is one of several locations in Golden Sun: The Lost Age that become available once Felix's party sets sail on Piers' boat, and so it does not have to be visited at a predetermined point in the game.
Geographically, Izumo is the Weyard equivalent of Japan. The only coastline is on the western side of the island. A mountain range down the middle of the island separates the city of Izumo to the west from Gaia Rock (known to the locals as Mt. Mikage) to the east.
The city of Izumo is located by the island's coastline. Izumo is similar to ancient Japan in architecture and customs. Its houses consist of wooden huts with thatched roofs. Izumo is governed by Lady Uzume.
There are two major things to do after clearing Gaia Rock. The first is to give the Dancing Idol to Lady Uzume; in exchange, she will give Felix Coal, a MarsDjinni. The second is the Izumo Catacombs. In order to enter the catacombs, Felix must use Move on the leftmost pillar in the ring of pillars to the right of Lady Uzume's house (later in the game Isaac and Garet can accomplish this instead), and then Sheba (or Ivan) must use Reveal to unveil the ladder in the center of the ring. Although the catacombs are available upon first arriving in Izumo, they are unavailable for exploration until Felix gains the SandPsynergy in Gaia Rock. The Phantasmal Mail can be found here, as well as the SummonUlysses. However, the room containing Ulysses remains unreachable until Piers learns Parch in Aqua Rock
Spoiler warning:The following section(s) contain plot and/or ending details that some people may not wish to learn before reaching this point in the game on their own. If this applies to you, take caution while reading this section (if you choose to read it at all).
Sometime before the party arrives at Izumo, the Serpent residing in Gaia Rock awakened (possibly a result of the Psynergy Stones scattered during Mt. Aleph's eruption, as are many of the obstacles encountered throughout the games). At the time, the people of Izumo were having a festival, which the Serpent promptly ruined. At some point Lady Uzume ordered barrels of Dragonsbane (which has an effect on the Serpent similar to catnip on cats) to be transported to the Serpent's lair deep within Gaia Rock. Supposedly, the Serpent demanded a female sacrifice each year, and so a lottery was formed to determine who the sacrifice would be. Kushinada, a close friend of Lady Uzume and her brother Susa, was chosen as the first sacrifice.The city's residents happily celebrate the slaying of the Serpent. Izumo at once becomes lively again.
Enraged, Susa travelled to Gaia Rock on his own in an attempt to destroy the Serpent before Kushinada could be sacrificed. Lady Uzume predicted that a great hero would come to slay the Serpent by the next full moon.
After the Serpent is destroyed, the townspeople are in much better spirits, and are even preparing another festival. A cutscene can be triggered by entering Lady Uzume's house, during which Kraden attempts to explain Psynergy to Uzume and Kushinada, and it is revealed that both they and Susa possess some level of Psynergy (most likely of the Venus element, which is later confirmed after defeating Gaia Rock). Also, Susa tries to deny having defeated the Serpent, but Felix and Co. point out that Susa greatly weakened the Serpent with the Dragonsbane (Sake in the Japanese version) and delivered the final blow with the Cloud Brand, making him an essential part of the Serpent's defeat.