- "This is a general term for the region in the southeast part of Angara that includes Ayuthay, Kaocho, Sana and Champa. It is generally a sophisticated and prosperous area. This prosperity can be traced to several Alchemy Machines."
 Background and Story
The Ei-Jei region contains a number of countries of diverse origin. Ayuthay and Passaj both possess long histories, being home to the Exathi, a race of skill craftsmen dating back to ancient times. The country of Sana arose after the Golden Sun event, and would initially found Kaocho as a colony, though Kaocho would break off into its own kingdom. Champa is home to a number of pirates, and existed for an undefined period of time prior to the Golden Sun event.
Initially trying to head to Bilibin, Matthew's party is forced to travel to Ei-Jei when the first route is blocked by the emergence of a Psynergy Vortex that breaks the usual method of transport. When they detour to the Konpa Ruins they are attacked by Blados, Chalis and a Masked Man. These antagonists kidnap Rief and force the party to take the southern route, prior to immediately triggering a landslide, making the ruins impassible from the south. This forces Matthew and co to power up the Alchemy Forge and Alchemy Well to travel north via Craggy Peak from the town of Passaj.
Most of the Ei-Jei region falls under the shadow of the Grave Eclipse. Due to the Alchemy Machines, Passaj, Ayuthay, and Harapa are mostly unharmed. Meanwhile, Kaocho is almost completely destroyed. Champa's people manage to escape, but are forced to burn their homes to ward off the attacking monsters. Only Sana's capital city of Tonfon is completely unaffected, lying outside of the Eclipse's shadow.
The politics of the Ei-Jei region are fairly complicated. Passaj and Ayuthay are closely allied, in part due to their shared heritage. Kaocho has imperialist views, and has attacked both cities, with varying levels of success. Harapa is noted to be fairly independent; being a city of ruins, few rulers had any interest in the city. However, they do seem to be on good terms with both Passaj and Ayuthay.
The country of Sana was once a large empire, with Kaocho being a colony. Recently, a civil war caused a change in leadership, leading to peace, but at the cost of most of Sana's colonies. Kaocho would become independent, and is led by King Wo, leader of the losing faction of the war.
Champa, being a pirate nation, is feared by many in the region, particularly those who run trade ships in the Sanan Sea.
 Name Origin
The Japanese name of the region, Ei-Jie seems to correlated with the Japanese name of the Jenei, Jienese. One possible reading of the element 'Ei' would be descendant, scion, or lineage, suggesting that the region's general name refers to it being the home of the "Lineage of the Jienese" or Jenei: it is a region rich with ruins made in-tandem by the Neox and Exathi cultures.