Garnet Dragon

Garnet Dragons (ガーネット・ドラゴン) are Raid Bosses and a dragon species above the Red Dragons and Flame Dragons. They are capable of using high-level dragon magic to take humanoid forms.

KR contracted with a female Garnet Dragon at some point in time, whom he nicknamed Ga-tan (ガーたん). After breaking his original contract with her during the events of Go East, Kanami!, he reforges one using his Overskill, Crimson Contract. Due to a shortage in magic supply, Ga-tan cannot maintain her dragon form for long periods of time. Ga-tan's birthday is June 24.

Appearance
Ga-tan has two forms; a dragon form and humanoid form. In her dragon form, Ga-tan is a 25m-long crimson dragon with translucent scales made of flame. In her humanoid form, Ga-tan takes the shape of a young girl with exposed dragon ears, wearing a white dress, a white hair ribbon, and a set of bead earrings.

Personality
Ga-tan, despite her child-like appearance, is very old and speaks in an antiquated fashion. Despite her abusive behavior towards KR, which includes casually breaking his ribs to wake him up, she sticks around him even though she no longer has a contract with him aside from the Crimson Contract.

She is rather passive about the events going on around her, holding little interest in the dilemmas and trappings of Plant Hwyaden and seeing the Holy Empire Westelande as an insignificant force that can only control half of a tiny island. However, she does acknowledge that there are people not to be underestimated there, and remains by KR's side because he has unexpected wisdom behind his silly facade.

Prior to the Catastrophe
Ga-tan originated from the Northern Ridge Rus' (北稜ルーシ). It is likely in the Russian server as references to the real-life Northern Ridge and Kievan Rus', but this has not been confirmed. Compared to Northern Ridge Rus', Yamato is a "tiny island to the Far East" in her eyes.

Go! East! arc
After Kanami, Coppelia, and Elias Hackblade go on to challenge the Genius without Leonardo, KR uses Castling to bring his physical body from the Yamato server to the Zhongyuan server and participate in the battle. He summons Ga-tan after motivating Leonardo to participate in the fight, and they ride on her back to go confront the Genius. Leonardo uses himself to knock Papus and Rasphuia off the Black Dragon, allowing KR and Ga-tan to take on the Black Dragon alone.

Because contracting with the Garnet Dragon reduced her stats to a Minion-level monster's, KR destroys her contract by contracting with a thirteenth monster (over the twelve contract limit), reverting her to her Raid Boss status. He then re-contracts with her using Crimson Contract, allowing her to retain her original stats and maintaining equal ground with the Black Dragon. Although they manage to kill the Black Dragon, KR succumbs to the injuries sustained during the battle and resurrects in Minami, after which he joins Plant Hwyaden.

Around the time of The Larks Take Flight, KR informs Ga-tan that he told Kazuhiko about Kanami's impending return to Yamato after she forcibly awakens him by breaking his ribs. He reveals that he has no interest in Plant Hwyaden or the events going on in the server, and that he was only waiting for Kanami to come back. Ga-tan herself has gained an interest in the events on Zhongyuan, after having witnessed the convergence of four great powers: the protection of dragons (herself), the blood of the fairies (Elias), the principle of transmigration (possibly referring to Rasphuia's ability), and the skills of the great ones (Kanami, Leonardo, and KR's Overskills).

Homesteading the Noosphere arc
Ga-tan is seen in her human form during the invasion of the Eternal Moths. Instead of helping in fending them off, both she and KR simply sit back and wait for Shiroe's raid to finish.

Trivia

 * KR's Overskill is named after Garnet, who is also known as the "Crimson Princess."
 * Ga-tan seems to be a reference to Alexstrasza the Life-binder from the popular MMORPG World of Warcraft.