Yuna

Yuna (ユーナ) is a character from the Mega Man Legends series. She is the Mother Unit who rules over the systems on Terra. She is accompanied by her Servitor Unit named Gatz. She is indirectly responsible for awakening Sera when Mega Man Volnutt defeated Rush Mammoo to rescue Sulphur-Bottom, whose engine had been damaged by her and Gatz.

Before Mega Man Legends 2
A long time ago, after the Master's death, MegaMan Trigger (Mega Man Volnutt) fought against the System to destroy it and fulfill the Master's dying wish, fighting against Yuna, Sera, and others. As time went by, Yuna slowly came to understand what Mega Man was trying to do, and decided to take a neutral position by neither helping nor fighting against him. Sera, frustrated with Yuna's decision, travelled to Terra herself to fight against Mega Man, and the two fought each other to a standstill as Sera wasn't able to bring her full power to bear outside of Elysium, both expending all of their energy and Mega Man's original body almost totally destroyed. After the battle, Yuna took that opportunity to seal both inside stasis fields, with Sera being imprisoned with Geetz on Forbidden Island while Mega Man was "reset" and sealed with Data on Nino Island.

As time passed, these events were remembered by the Carbons as an old legend about two goddess that watched the world, the sky goddess (Sera) who "guards the record of the ages" and the Earth goddess (Yuna) who "guards the keys". When the sky goddess tried to borrow the keys from the Earth goddess, they argued, and the sky goddess was imprisoned by the Earth goddess on Forbidden Island.

Yuna watched over Forbidden Island since then, warning people to not approach the island and saving Diggers that went there by putting them into hibernation. 30 years before the events of Mega Man Legends 2, she saved Barrell Caskett and Verner Von Bluecher when their ship crashed on the island during an expedition. 20 years later she found Matilda dying from injuries sustained while trying to explore the island with her husband. Yuna used too much energy and parts of her body trying to save Matilda with her nanotechnology; so much so that she wasn't able to move anymore, and had to "borrow" Matilda's body until her body was repaired, which she placed into Matilda's Dropship. From that point on, Yuna inhabits Matilda's body.

Mega Man Legends 2
In the beginning of Mega Man Legends 2, Yuna infiltrates the Sulphur-Bottom disguised as a reporter to warn the people gathered there that the Mother Lode isn't a treasure, but "a catastrophe waiting to happen". Regardless of her warning, Von Bluecher chooses to continue onward. Yuna asks Gatz to attack the Sulphur-Bottom as a further deterrent, but the attack damages the engines and the Sulphur-Bottom slowly plummets towards Forbidden Island. When Mega Man went to Forbidden Island to find the Sulphur-Bottom, Yuna's original body can be seen in Matilda's Dropship, as well as several Diggers in hibernation. After Sera is awakened accidentally by Mega Man (Although that she and Gatz are responsible since they made the ship plummets towards Forbidden Island that causes Mega Man to awaken Sera to stop the storm), Yuna's original body is taken away from the island and the Diggers are returned to Yosyonke City.

After the four keys to the Mother Lode were found by Mega Man and consequently stolen by Sera and Geetz, Yuna appears to help Mega Man and argue with him. After Geetz's defeat, Mega Man was damaged and Yuna repaired him with Data's help, learning why Mega Man wanted to destroy the System. She helps Mega Man to reach Elysium and stop Sera, guiding him throughout Elysium. After Sera's defeat, Yuna convinces her to save her own life by transferring her primary program to Yuna's original body. The game ends with Yuna (in Matilda's body), Sera (in Yuna's original body) and Mega Man in Elysium, without any means to return to Terra and the Elder System starting to awake.

Trivia

 * Yuna's name is derived from "uno", the cardinal number "one" in Spanish.