|Alias|| Knight King (騎士王, Kishiō)|
Idiot (バカ, Baka)
|Birth Date||July 10th (Cancer)|
|Affiliation||8th Special Fire Brigade|
|Rank||Fire Soldier (Second Class)|
|Manga||The Devil, The Knight, and The Witch|
Arthur is a young man of average height with shaggy blonde hair and blue eyes. He tends to style his hair upwards into a ponytail when in a fight, so that his field of vision would be clearer. When Arthur was first introduced, he wore a dark jacket, with a button on his collar, shaped like a cross-like insignia, light shirt, dark pants, a belt and dark shoes. He was later presented with a bunker gear, a protective outer jacket and trousers. Arthur carries a scabbard alongside him, in which he keeps his blade-less sword. Parts of his outfit, are coated with blue lines. Arthur wears a dark green jumper with a hoodie, which he puts on his head instead of a helmet. The buttons of his protective jacket are in the shape of cross-like symbols. Arthur's outfits contain patches with "8" on them, to signify his affiliation to the 8th Special Fire Brigade. He also dons a neck protector and protective gloves. When attiring the 8th bunker gear, Arthur chooses not to wear the helmet, as it doesn't fit the image of a knight.
|“||We meet again, murdering demon. You... I'll... Whet... Blade... Bones... Hmph.||”|
|— Arthur Boyle to Setsuo Miyamoto in The Battle Begins|
Arthur is confident in himself as a Third Generation, though he can be somewhat arrogant, cocky and full of himself at times. He has a medieval-like complex, referring to the girls he meets as princesses and the Special Fire Cathedral 8 as his castle. Arthur sees the world in a different light; he believes the pigeons to be griffons and that he was successful in slaying dragons. According to Shinra, he is inexplicably popular and seems to always have a silent and mysterious façade, though Shinra thinks he's just too stupid to articulate anything. Arthur often bickers with Shinra Kusakabe on who are superior: knights or heroes. He prefers to go his own way, rather than do things the way other people think he should. Arthur takes great pride in Excalibur. Due to his attitude and casual demeanor, Arthur tends to make bad impressions on people. He was shown not to be bothered by human antics. Despite his repetitive bickering with Shinra, Arthur is capable of putting the differences between the two aside and work as a team. Arthur is usually nonchalant even while struggling in fights. As well as this, Arthur has repeatedly been referred to as foolish and lacking in common sense. Like the other brigadiers, Arthur has a high sense of justice, which he correlates to his persona of being a knight. Arthur has a habit of repeatedly saying "Hmph" in response to people, coming across as stubborn. Arthur has a tendency to mock his fellow brigadiers in a joking way.
Arthur is a Third Generation, who has exceeded the abilities granted to him and is able to raise the temperature of the flames he creates, therefore allowing him to fabricate and control plasma. His capability in doing so has made various individuals identify him as having a strong will of fire. By manifesting plasma on hilt-like objects, Arthur is able to weld, cut through metal, and generate electricity. He mainly uses this ability on his sword Excalibur, which he exclusively uses in his right hand, though he can also use it in his left with greater less effectiveness. Using the sword, he can deflect and fend off against flames. He also possesses incredible raw physical strength, being capable of repelling a Flame Human with a single punch. 
Arthur attended the same training academy as Shinra, where the two were introduced to each other and often bickered over their beliefs.
Introduction arc Edit
Arthur arrives at the Special Fire Cathedral 8, where he runs into Shinra Kusakabe and the two begin fighting. As their fight is taken to roof, he meets Iris and Maki Oze, followed by Takehisa Hinawa, who instructs him to spar with Maki in order to test his abilities. Unable to beat her combat skills and ability, Arthur gives up. After eating at Ippudo Ramen, Arthur is offered a battleaxe, but refuses to take it. When the brigade is notified of a Flame Human in the Iriya District, he departs to the scene. While on route, Akitaru Ōbi instructs Arthur and Shinra to conceal their weapons in public, much to his confusion. After their arrival, Akitaru pulls the two aside for disobeying orders, where Arthur questions the instruction, leading Akitaru to justify his reasoning. After their conversation, a burst of flames emerges from the apartment, prompting the brigade to storm the building and find the Flame Human. Arthur volunteers to put the man out of his misery and impales his core. Immediately after that, the ceiling begins to collapse, but the brigade escapes unscathed.
Arthur participates in the Rookie Fire Soldier Games. When the simulation exam starts, he charges towards the building and uses his sword to slice his way in. After one of the entrants bombards the building with his ability, Tamaki Kotatsu falls onto him, which gets the two into an intimate situation. Following his beliefs, the boy allows Tamaki to take the lead when exploring their current location. When the two are attacked, Arthur jumps in to defend the girl. He then charges in, believing Joker to be part of the exam, despite Shinra's warnings, but does not land a single blow. When the man uses an unknown substance to put their lives in jeopardy, Arthur uses his sword to cut a hole in the ceiling, allowing Shinra to evacuate them all to safety, with Arthur being caught by his team-mates in a blanket.
The following day, Arthur accompanies Shinra on his mission to rescue a dog, who was reported to be stuck in a tree, and afterwards, helps Mamoru hand out balloons to children. The two then learn of an accident in the courthouse from Takehisa, who was moving to the scene with the rest of the brigade. Grabbing a lift from Shinra, the two Fire Soldiers face Setsuo Miyamoto, with Arthur hitting the opponent with a backwards fist and delivering a collaborative attack alongside Shinra. When the brigade catches up to Shinra, Arthur and the rest find themselves in a confrontation with the 5th Special Fire Brigade. Tōru Kishiri mocks Akitaru, which leads to Shinra and Arthur jumping in, but Maki and Takehisa detain the two. A stand-off between the brigades is then catalyzed, but the two depart without any signs of struggle.
VS. 5th Special Fire Brigade arc Edit
The following day, Takehisa begins training the Fire Soldiers, having Arthur spar against Maki. Later, after Iris has gone missing, the the 8th Special Fire Brigade infiltrates the 5th Special Fire Fighting Industrial Complex, where Arthur finds himself in a fight against Setsuo, who was modified by the 5th Special Fire Brigade. Mid-way into the fight, Arthur realises the whole time he had been fighting with Excalibur in the wrong hand, which is why he had been struggling so much. Before Setsuo could execute his final attack, Arthur finishes him off in a dash with Flash of Lightning, successfully exterminating him. After the two brigades ordeal ended, a dinner party was organized between them as a sign of reconciliation. As Maki created some of her Pusu Pusu and Mera Mera, Arthur sliced all of them in half, stating that Takehisa told him to destroy them whenever she creates them.
VS. 1st Special Fire Brigade arc Edit
Later at the brigades church, Akitaru instructs Arthur and Shinra to infiltrate the 1st Special Fire Brigade and uncover any secrets they may be hiding. A while later, the two and Maki arrive at the 1st Special Fire Fighting Cathedral, along with Tōru Kishiri and Takeru Noto. As they walk inside, they meet Karim Fulham, followed by the other Company Commanders and Battalion Commander of the 1st. When Burns agrees for the newcomers to test their abilities, they go out the courtyard and begin sparring. After Rekka and Takeru's fight, Arthur and Shinra confront Burns. Confident that he will defeat Burns, he charges at him heroically, but to no avail, as Excalibur is blocked and repelled, much to Arthur's confusion. Afterwards, Shinra tries his luck against Burns but is also defeated with ease, and the newcomers are welcomed to training with the 1st for the month.
On the fifth day of training, the brigade is notified of the appearance of Flame Humans, and departs with Shinra in the Fulham Company to the scene. When they arrive, Karim instructs the two to stay put, which they do, until Shinra notices a priest creating an artificial Flame Human and takes chase after the culprit. As they stumble across Karim and Rekka, Arthur spontaneously confronts them about it, but is quickly subdued by Shinra. After the mission ends and they arrive back at the Cathedral, Arthur, still annoyed at Shinra for stopping him, questions why he did so. Shinra explains that by confronting them in the alley would have led to their defeat, as they were outnumbered by the amount of 1st Brigade members. The two then resolve a plan to infiltrate and investigate Rekka and Karim's room, starting with Karim. As they arrive, they discover the same Bug used to create the artificial Flame Human, but at the same time are discovered by Karim. As Karim points out he is on their side, hiding the Bug on purpose to lead them there, he reveals that the real criminal is Rekka. A little while later, Arthur and Shinra await Karim in the corridors, and ask for permission to help with the capturing of Rekka, to which Karim tells them to do what they like.
Preacher Pursuit arc Edit
Upon arriving back at his brigades church, Akitaru has the Soldiers look through their mission records to find any leads on the Preacher and White Hoods. After Shinra reveals his brother is affiliated with the Preacher, Arthur questions the reliability Joker's information that he gave to Shinra.
Asakusa arc Edit
Following a lead on the Preacher, the trail leads the 8th to Asakusa. Meeting up with the 7th Special Fire Brigade, their meeting is cut short when a Flame Human appears within the district. As Benimaru Shinmon deals with the matter, Arthur questions how the brigade commander is manipulating flames, which Konro informs the 8th that he is a second and Third Generation. In the aftermath of the event, the 8th assists in the reconstruction of the destroyed houses, with Arthur welding materials together. After Hikage is revealed to be an importer, Asakusa irrupts in flames. Akitaru instructs the 8th to assist the villagers evacuating, but they are immediately attacked by a flaming arrow. Shinra and Arthur then begin searching for the shooter.
When Shinra is attacked by a pair of White Hoods, Arthur defends him from Arrow's attacks, as the two groups fight each other. Realising they need to start coordinating their attacks with one another, the Fire Soldiers manage to get the upper hand. When Arthur corners Arrow, Haran intervenes and gets slashed by Excalibur. Wounded, Haran swallows a Bug and transforms into a Flame Human. With his new found strength, Haran overpowers Arthur and the Soldiers are engulfed by his fire ball. Jumping back into the fight, Arthur attempts to cut his horns, but is unsuccessful, before being repelled again.
Vulcan's Workshop arc Edit
After the brigade returns to their church, Akitaru tasks Arthur, Shinra and Iris with going to Vulcan's workshop to make a good impression on Vulcan. Upon arrival, Arthur announces his presences, which leads to him being attacked by flames and cans. The group are then met by Yū, who manages to get them into the workshop. Afterwards, everyone in the workshop goes outside, where they witness a projection that Vulcan made. Shortly after, the Ash Flame Chivalric Order arrive at the workshop, leading to Vulcan making Arthur a knight's arsenal in order to fight the group. Outside, he meets Flail, and attacks the group with his make-shift Excalibur, resulting in all but two of the white hoods dissolving. After, he fights Flail and slices thought his Ignition Ability. When Mirage makes a mirage of Arthur, he becomes sadden by his attire, followed by Flail attacking him. Standing back up, Arthur wows to not forgive Flail for destroying his steed.
- Arthur shares his name with Arthur Pendragon, whose weapon of choice was also called Excalibur.
- Arthur was first seen on the cover page of Chapter 0, despite not debuting until Chapter 2.
- According to his Character Profile in Hero or Devil:
- Arthur's favourite food is royal court cuisine (which he hasn't tried before) and ramen from Ippudo Ramen, while his least favourite food is horse meat.
- Arthur's favourite music is court music, even though he has never listened to it.
- Arthur's favourite animal is a horse.
- Arthur's favourite colours are white and blue.
- Arthur prefers people with glass shoes and tiaras.
- The person Arthur respects the most is King Arthur.
- Arthur's hobby is making castle models, his daily routine involves sword practice and his dream is to become the Knight King.
- Arthur's foot size is 26 cm and his eyesight is 1.5.
- Arthur's favourite school subject is physical education, while his least favourite is one that involves a classroom.