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 Rauli 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 fiancees later participated in the Pruning Ceremony to support the Rauli 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 Astal 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 Rauli 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
- Rauli 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 Rauli 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.
- Balm Tribe - A male only tribe that normally opposes the Rauli Tribe.
- Ruluch Tribe - A Tribe that competed in the Pruning Ceremony. They are skilled in martial arts, but when two of their members fall sick, they are replaced by Rengetsu and Sonia, who quickly befriend Touya. The tribe loses to the Rauli Tribe.
- Jaja Tribe - Also known as the Judgement Tribe. They are the only tribe who are allowed to live at the base of Great Deity Tree.
- Panau Tribe - The tribe who won the previous Pruning Ceremony
- Remna 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 Treelord) as well as to establish one new law within the Great Sea of Trees only if it is approved by the Great Tree Deity.