Gimmy Adai is a boy from Adai Village who was cared for by Rossiu Adai. He is the older twin brother of Darry Adai, with the pair being orphans who had no parents to care for them in their underground home. When the population of their village exceeded its limit of fifty people, the village elder chose Gimmy and Darry to be the two individuals sent to the dangerous surface, as they had no parents. Rossiu decided to accompany them to ensure their safety, and the three subsequently joined Team Gurren.

In terms of appearance, during the early part of the story, Gimmy has orange hair that falls straight down around his face, framed by a lock of hair between his eyes. He wears a brown cloak over a black shirt and blue pants with brown shoes. In the later part of the series, he has grown significantly, his hair becoming a bit wilder while retaining the distinctive lock between his eyes, and he wears the standard Grapearl squadron uniform.

Gimmy's personality is defined by being the more impulsive and outgoing of the twin siblings. In his younger days, he is almost always in a joyful and cheerful demeanor, often serving as comic relief alongside his sister. As he grows older, he becomes more mature and is deemed capable enough to pilot his own Grapearl. Despite this growth, he retains a tendency toward recklessness that can sometimes get the duo into trouble. During the intense battles against the Anti-Spiral, Gimmy shows significant emotional vulnerability, being deeply distraught over the losses of his friends in Team Dai-Gurren, particularly Jorgun and Balinbow, who sacrifice their lives to save him and Darry. He also experiences fear when the Super Galaxy Dai-Gurren becomes trapped in a pocket of ultra-dense space, wanting to join the fight but finding himself unable to overcome his terror.

Gimmy holds naive beliefs about the extent of Simon's power, initially thinking that Simon could bring any deceased person back from the dead due to his colossal Spiral Power. He questions why Simon accepts losses instead of resurrecting fallen comrades. After a brief explanation from Yoko and further elaboration from Simon, Gimmy comes to understand the truth, and this moment of growth leads to Simon finding him worthy of inheriting the Lagann.

The bond between Gimmy and Darry is exceptionally strong, and they are often seen together. They are frequently left to their own devices around the Dai-Gurren, except when in the company of older female characters such as Yoko or Nia. In the second part of the story, seven years after the fall of Teppelin, Gimmy and Darry have become important pilots in the Grapearl squadron, often fighting together as a team. Together, they manage to apprehend Viral when he returns seeking vengeance, arresting him and taking him to jail. When Mugan attacks first strike Kamina City, Gimmy and Darry attempt to stop them but fail. However, during the first space battle, they successfully protect the city during evacuation efforts. When the Arc Gurren-Lagann is formed, Simon entrusts Gimmy and Darry with taking over the controls so he can stop the Chouginga Dai-Gurren.

Throughout the conflict in space against the Anti-Spirals, Gimmy continues to fight alongside his sister. When Darry is shot down after exploding a missile to save everyone, Gimmy rescues her. Later, when speaking with Kittan, Gimmy asks how he can continue to fight after so many deaths, and Kittan yells back that Jorgun and Balinbow saved them precisely because they believed in the twins.

Gimmy's notable abilities center on his piloting skills. He is deemed mature enough to pilot his own blue Grapearl, and later proves himself worthy of inheriting the Lagann's Core Drill from Simon. In the epilogue, which takes place twenty years after the main story, Gimmy is seen alongside Darry not only as commanders of the Grapearl squadron but also as the new pilots of Gurren Lagann itself. His name is derived from the Japanese word migi, which means right.