Gaira is a former member of the Earth Conquerors and is known as the Green Gargantua. Gaira was captured in China but escaped and fought Varan in 2010. He soon reunites with his Sanda and the two face off against Godzilla but they aid him and other Kaiju later in The Trilopod War. Gaira is persuaded to join the Earth Conquerors by SpaceGodzilla. However after Sanda is severely wounded by the other Conquerors, he leaves the faction and joins with the Earth Defenders.
Gaira resembles a humanoid giant with green skin and green fur. The fur hangs loose and somewhat resembles sea weed. The top of his head is flat and his eyes are yellow with red pupils. His nose is very large and wide. Gaira has an under bite, with two fangs on the lower jaw extended outwards. He has sharp almost claw like fingernails on his hands.
In the past, Gaira was very much like his brother Sanda and was curious of humans. However, after he was captured, held captive and tortured by the Chinese military, he developed a deep hatred and a grudge towards humans and is much more savage when in battle than Sanda.
Despite he and Sanda not being able to see eye-to-eye and sharing a sort of rivalry, he does genuinely care for his brother and will protect him from harm, like when he saved him from being hit by Godzilla's Atomic Breath in Brisbane. When Sanda took the force of Dagahra's Irabushan Beam attack to save Gaira, the Green Gargantua is shown to be worried and scared for his brother's health. When Sanda is among Fairy Tail's and the Earth Defenders' wounded, he never leaves Sanda's side.
Upon his departure from the Earth Conqueror faction, Gaira showed great hatred towards his former allies for what they had done for his brother and the way they forced him to join the faction. He allied himself with the Earth Defenders, no longer holding any grudge against them as they helped him in defeating Dagahra and Ganimes. He also seems to no longer harbor any hostility towards Fairy Tail either as they have also helped him, the first time Gaira seems to have a good relationship with humans. The Gargantua also seems to have developed a slight friendship with Elfman Strauss, discovering that the two have something in common.
Not much is known about Gaira's past though it is theorized that both he and Sanda were born in 1966. 1967, Gaira and Sanda where spotted by humans in China as children and where mistaken for cryptids known as Yeren (Or Chinese Wild Men). A Monarch team was sent to China to investigate the sighting. The young Gargantuas saw the Monarch camp and out of curiosity, emerged from the forest and meet face to face with a Monarch scientist, Akami Towaga. Akami gave the young Kaiju food, who thanked her food the gift before returning back to the forest. The same Monarch team attempted to track down the Gargantuas over the years. Both Gaira and Sanda managed to avoid the team through said years way up to adulthood.
In 2002, Gaira was captured temporally in Korea and was experimented on but managed to escape and destroy his captors before making his way to China. After Korea sent a distress signal, the military of China created a trap lure Gaira before capturing him. The Chinese government also bard Monarch from investigate the Gargantuas. The humans held Gaira in a military against his will and to use him as a weapon, which gave birth to his deep grudge towards humans.
Immense Strength: Despite his smaller size compared to the majority of Kaiju, Gaira is extremely tough. In physical strength he was able to overpower Varan to the point he was forced to retreat. He is tenacious enough to attack Godzilla head on and when teaming up with Sanda and Anguirus, was able to kill a Trilopod or two. His claws are shown to be able to cut through Godzilla's skin and leave a deep gash. His fangs can also pierce Godzilla skin as well. He is quite a strong swimmer compared to his brother. He is strong to lift Varan by the head. He is also able to improvise weapons such as a radio dish or a molten rock.