Flame is a small digital humanoid being. When not in a solid form, his body is red prism-like data. Like Ai, a fellow Ignis, Flame has markings over his black body, which is tinted red, in red flame shaped markings and thicker lines than the lines on Ai's body. He has yellow eyes that are semi-oval, giving him a more mature appearance. His body is notably more slender than Ai's body with more boot like feet and wisps on his head that resemble the flicks of a flame. In stature, Flame is one of the taller Ignis, being the same height as Ai and shorter than Earth. When overexcited, he becomes a fire demon, but he doesn't enlarge.
When peering out of Takeru's Duel Disk, he takes an eye form nearly identical to Ai's. The lines are red and the iris is the same yellow as his eyes.
Unlike Ai who is quick to panic or pull jokes, Flame is normally a level-headed Ignis who speaks with an even voice and is very straightforward. He is very calculative, keeping track of how many times he's told his introduction to Takeru (37 times exactly). However, when overconfident, he tends to burst into flames, usually with a flame on the wisp of his head. Flame also has the tendency to flaunt his partner in front of opponents and over-exaggerate their words, seen as he says to Bit and Boot that Soulburner (Takeru) will give them a crushing defeat. He can be a bit egotistical (always explaining the kanji used in his name and calling it cool) and appears to be a risk taker because of his Skill.
Like Ai, Flame trusts and believes in humans. Having been inspired by Playmaker's victory against the Knights of Hanoi, Flame followed in his footsteps by finding and teaming up with Takeru. He also recognizes that there are good and bad humans compared to Earth, Windy, and Lightning, who resent humans either way. Despite his ego, Flame does show that he cares about those that he considers allies, shown in the Duel against Ryujiro and Flame helps Takeru overcome his trauma during the Lost Incident and when Flame and Ai express genuine interest in understanding Yusaku and Kolter's backstory. When confronted by Lightning about his stance, Flame firmly says there are no sides, showing how he and Takeru both want humans and Ignis to coexist peacefully.
Much like Ai, Flame has a hard time understanding sarcasm and rhetorical questions, as such he tends to take everything Takeru says literally much to the latter's annoyance. Despite being more mature than Ai, he has a small interest in human technology that make him subtly childish, such as on the Ferris Wheel (he claims logical reasons for using the ride for a private conversation, only for Ai to point out that he just wanted to ride it) and when he suggested adding wheels to Takeru's Duel Disk after seeing Ai fly. Also similar to Ai, he is loyal to the Ignis (until he learns about Lightning's betrayal) and his partner, whose potential is why he supports coexisting with humans.
In addition, like Ai, Flame also shows care towards his fellow Ignis, as he quickly saved Ai (and Playmaker) after they were trapped by Lightning and when he attempted to save Windy's data as he was being deleted by Lightning.
Despite being the FIRE Ignis, Flame is actually very calm and level headed in tough situations. He also seems to be able to control his anger, as seen when despite vowing to take Lighting down for destroying Cyberse World he knew to escape when he and Soulburner we surrounded by the Bit and Boot clones. He is even willing to work with Varis to stop Lightning, despite the latter's attempt to destroy the Ignis. He even managed to help Takeru understand Varis wanted to apologize for what his partner endured during the Hanoi Project.
Flame also has a tendency to be very blunt, often pointing out the mistakes of both Ai and Takeru, much to their annoyance. He can be a bit prideful, ignoring Takeru whenever he feels embarrassed. He also likes to be praised, seen as he blushes when Ghost Gal calls him cute.