Great Sea of Trees (大樹海 Dai Jukai?) is a major location in the series.
The Great Sea of Trees is located between the Kingdom of Mismede and the Region of Sandora. The Rauri Tribe village within the Sea of Trees was attacked by a Intermediate Class Phrase in the form of a giant spider but thanks to Touya and his friends they were able to defeat it but not without heavy casualties and injuries.
Touya and his fiances later participated in the Pruning Ceremony to support the Rauri Tribe. After the Pruning Ceremony, all the tribes were attacked by giant wood golems.
The people of the Great Sea of Trees would later be attacked the order of magic beast warriors of the Kingdom of Sandora, with the sole purpose of capturing the people there in order to increase the number of slaves they owned after the destruction of Astral City. The people that were captured as a result of this attack were later freed and returned to their homes after Touya freed them.
- Pam: The current matriarch of the Rauri Tribe who currently rule over the Great Forest Sea
- Great Tree Deity: The god of the region.
Locations within The Sea of Trees
- Great Deity Tree: The largest tree in the Great Sea of Trees. It also serves as the area where the Pruning Ceremony is held every 10 years.
Tribes of the Great Sea of Trees
- Rauri Tribe - A female only tribe that are the current winners of the last Pruning Ceremony
- Rivet Tribe - A tribe of the Great Sea of Trees that specializes in using poison. After their defeat at the hands of the Rauri Tribe they attempted to take the power of the Great Tree Deity through the use of specially created Wood Golems, but they were defeated by Yumina and Linze in Frame Gear units outfitted with the new Fragarch system.
- Balum Tribe - A male only tribe that normally opposes the Rauri Tribe.
- Jaja Tribe - Also known as the Referee Tribe. They are the only tribe who are allowed to live at the base of Great Deity Tree.
- Panao Tribe - The tribe who won the previous Pruning Ceremony
- Lemuna Tribe - One of the tribes that competed in the Pruning Ceremony. They were defeated by the Rivet Tribe.
- Every 10 years, a competition called the Pruning Ceremony is held between the tribes to decide who the strongest tribe (known as the Tribe of Tree King) as well as to establish one new law within the Great Sea of Trees only if it is approved by the Great Tree Deity.