The Flame Dragon is the secondary antagonist of the first story arc of the manga and anime Gate: Thus the JSDF Fought There, and the primary antagonist of Tuka's arc.
The Flame Dragon is a massive creature similar to depictions of dragons in Western fantasy. While smaller dragons are used by the Empire is battle, the flame dragon is far too large and powerful to be tamed. The flame dragon possesses to power to breathe fire, as its name suggests, as well as scales as hard as tungsten, which are completely resistant to the medieval weapons used in the Special Region, as well as assault rifle and even .50 caliber and 20mm autocannon fire. The only weapons capable of harming it are anti-tank weapons and heavy explosives. The dragon possesses massive wings which allow it to fly with great maneuverability, rivaling that of a helicopter. The only vulnerable point to arrows or gunfire on its body is the eye. Because of its great power, residents of the special region view it as a being with almost godlike power. Flame dragons are the apex predators of the Special Region, but are a very rare species, with only one adult and two juveniles encountered by the Japanese Self-Defense Forces since they arrived in the region. Flame dragons are extremely aggressive and will kill any living beings they encounter, and seem to be particularly hostile towards humans and similar beings such as elves.
The Flame Dragon seen in the Gate is first encountered by the JSDF Third Recon Team under the command of series protagonist Lt. Youji Itami in their first mission in the Special Region, where they witness it destroying an elvish village and rescue the lone survivor, an elvish girl named Tuka Luna Marceau. The JSDF aids the village of Koda in evacuating before the dragon arrived, meeting two additional characters who later become friends of Youji and the team, Lelei La Lalena, a sorceress-in-training, and Rory Mercury, an apostle of the war god Emroy and self-proclaimed demigoddess.
The dragon attacks the convoy of refugees, and is engaged by the Third Recon Team. Automatic weapons fire proves useless against the dragon, and the team only barely manage to drive it off by shooting it with a Panzerfaust 3 rocket launcher, blowing off its leg and force it to fly away in defeat. In spite of their victory, the refugee convoy lose over 100 men.
The dragon is next mentioned by Yao Haa Dushi, an elf who seeks the JSDF's aid in slaying the dragon. At the same time, Tuka shows signs of PTSD, as well as the delusion the Youji is her dead father. The JSDF refuse to aid in slaying the dragon, as they would be forced to violate the territory of a kingdom they had no treaty with, Elbe.
Youji, however, goes AWOL with Tuka, Lelei, Yao, and Rory, bringing with him several pounds of C-4 explosives and ten Panzerfaust 3 rockets. Upon arriving at the Yao's homeland, Youji's party place the explosives at the nest of the dragon with the help Yao's clan, however, the dragon returns and attacks them, killing all of the elves except for Yao.
The dragon manages to evade all ten rockets, and, to make matters worse, it is discovered that it is the servant of Giselle, the apostle of the underworld Goddess Hardy. Rory fights with Giselle while Lelei, Youji, and Tuka deal with the dragon. Lelei uses her magic to accelerate the swords of the fallen elves at the dragon, severely wounding it and driving to charge right over the C-4 laid by Youji. Tuka then its it with lighting magic, detonating the C-4 and killing the dragon in a massive explosion.
Shortly afterwards, Youji returns to Rory, to discover Giselle had severely wounded her. While Rory's regeneration powers allow her to recover even after the loss of her arm, she and Youji are surrounded by two juvenile flame dragons also in service of Giselle. Fortunately for Youji and Rory, the JSDF arrive, having signed a treaty with king Duran of Elbe, who it is revealed was one of the men wounded in the Empire's crushing defeat in the Battle of Alnus Hill, but recovered thanks to modern medicine brought by the JSDF. The JSDF bombard the two dragons with artillery fire and missiles fired from F-4 Phantom jets and Cobra attack helicopters, killing both of them and severely wounding Giselle, who is taken into JSDF custody.