I'm not a coward... But I know I have to be stronger...
Arc is one of the four Warriors of Light introduced in the Final Fantasy III remake. Like Luneth, he is an orphan from the town of Ur, to the point that he and Luneth were raised as brothers. However, Arc tends to get bullied a lot, eventually leading him to go to the nearby town of Kazus to prove that ghosts aren't real.
Arc, much like Luneth and Ingus, is in fact based on a character from the Famicom version although, like the latter, he is based on an NPC; Outside of Kazus is a man camping out who gets spooked when the party approaches him, mistaking them for ghosts. While Luneth meets Arc in Ur, the spot in which Arc actually joins is very close to where this NPC was and similarly has Arc being jumpy.
An unused interaction with Desch reveals that Arc is 14 years old. As of the time of this writing, this has yet to be mentioned in other media.
The very first trait that the player notices about Arc is his cowardliness. Being the proverbial Luigi to Luneth's Mario, Arc begins the game being unable to stand up for himself as he's bullied by children who seem to be younger than him. He also shows a rampant fear of having to encounter ghosts, a fear that the unused text shows persists as far as the Wrecked Ship. Even when not particularly fearful, Arc has a bashful side, as seen in the unused text where Sara compliments his intelligence or when the rest of the party credits him with saving Saronia.
But Arc's more defining trait is his intelligence. Arc is the "smart guy" of the group and has a knack for picking up weakness in enemies. This is especially apparant in the unused dialogue where Arc more often points out weakness or gives general advice; Some of these were moved to the guests for the final game while others were cut entirely. He also picks up on oddities; He's the one who figures out the link between the Living Woods and Argus' men attacking Tokkul and an unused skit had him questioning why Gutsco wanted the Horn of Ice to begin with (answer: to get at the fire crystal).
In spite of his intelligence, Arc is not wise beyond his years. The unused text makes it especially clear that Arc can be juvenile when it comes to love, being easily fooled and, in one instance fooling himself. Additionally, Arc has a temper that can cause him to act out, with the unused Saronia text being the most stand out example.
Still, Arc is the Light of Kindness and there are times that he embodies this. He empathizes with Alus Restor and is determined to help him restore Saronia, later soothing Alus' concerns on the possibility of his father hating him. The unused text also has him speak quite favorably of Refia when she finds it hard to believe that a bard wants her as his muse.
Arc has an interesting trend with his portrayals, consistantly being portrayed as a mage and leaning heavily towards the Summon-related jobs.
Arc's signature job is the Black Mage: It's what he is portrayed as in the CG opening and both of his units in Brave Exvius are based on the job (with Arc's Freelancer outfit picking up traits of the job as he is awakened). In Memory of Heroes, Arc uses the Black Mage job until the party finds the Earth Crystal, at which point, he switches to Magus. Arc's equivalant is also implied to be Teol, the Black Mage from the Final Fantasy I storyline.
Arc's interest in summoning is surprisingly consistent. In III itself, an unused skit has Arc try feverently to get a summoner to take him on as an apprentice, in spite of how difficult summoning can be. In spinoff materials, he has a heavy focus on summoning in FFRK despite being a White Mage (here linked with Leviathan) while in Memory of Heroes, he becomes a Summoner when the party reaches the Earth Crystal. Of particular note is Bahamut: In the novel, Arc hears Bahamut speak to him as the party is fleeing from the dragon, the dragon telling Arc to call upon him when needed. During the final battle, Arc is able to hear Bahamut once more and summons him to attack the Cloud of Darkness. Given the implications of the novel, it is implied that this is due to Teol the Black Mage, who was the one of his party to realize that Bahamut meant them no harm and convince them to hear him out.
Arc is notable among the four protagonists for having a clear character arc (heh). His introduction sets the tone with Arc getting bullied by a bunch of children. Luneth appears on the scene causing them to flee, but when Luneth tries to help Arc he simply runs away instead. Arc decides to stand up for himself and goes over to Kazus to prove that ghosts don't exist. Of course, Arc is, in fact, a scardy cat and after Luneth accidentally spooks him, Arc decides to travel with him to be braver.
The second part of the storyline depends on when players trigger Topapa's fourth Mognet letter. The party returns to the Altar Cave to find the missing children, the same ones that teased Arc at the beginning of the game, trapped by bombs. After dispatching the enemies, the kids thank Arc, even saying they never expected to be saved by him of all people before giving him a crystal fragment containing the Onion Knight job.
Finally, there's the Saronia plotline. The party rescues Alus from a gang of ruffians and he and Arc become fast friends. Arc takes the lead narrativewise during this portion of the story and it serves to be something of a capstone for his character development, having gone from being bullied to protecting someone else from bullies.
Having grown up together, Luneth and Arc have a modest sibling bond. While the game does point out how they tend to be foils of each other, it doesn't mention that they can be on the same wavelength at times, especially when it comes to girls; whether it be being jealous of Desch for having his girlfriend fawn over him or somehow deluding themselves (and even Ingus) into thinking Unei is a sleeping Princess. It's implied early on that Luneth is in charge of protecting Arc and, for his part, shows that he can do so; Some unused (and actually translated) dialogue at the beginning of the game has Luneth patch up Arc's bruises with healing flowers, and in Gyshal, some unused (but not translated) dialogue has Luneth cheer Arc up after he gets tricked by a nearby sheperd girl.
That's not to say that it's all perfect, however. Luneth's flippant and prideful attitude sometimes causes Arc to call him out on stuff and when Arc leaves the party in Saronia, Luneth is the only one not worried, mentioning that Arc threw tantrums all the time in Ur. Still, Arc does rarely show that he can dish out what he can take, mocking Luneth during the Duster subplot.
Early on, Arc and Refia don't have much of an explicit dynamic; Arc isn't particularly nice to her, but he also doesn't actively drive her up the wall like Luneth and Desch do. That said, what little we do get primarily paints it as negative, at least to begin with. In particular, a recurring trend seems to be Refia getting mad at the boys only to get rebuffed; Arc defends Desch when Refia assumes that he just walked out on Salina, and when Refia points out that Unei is more likely to be an old crone than a beautiful princess, Arc merely assumes that she's jealous. Additionally when Arc has his tantrum in Saronia, while most of the focus is on Ingus, Refia is also included in his rant. But, all of this is contrasted with the Bard subplot in Duster where Arc encourages Refia to give the bard a chance, such as offering a gift. Arc compares Refia to a Maiden's Kiss (an item) or a Madra's Harp. He even stands up for Refia when Luneth teases her, saying that Luneth is shy and could use a lesson in honesty from Refia.
Arc and Ingus' dynamic depends on what perspective you view it from. From Ingus' perspective, it's clear that he's looking out for Arc, most notably chastising Luneth for mocking Arc. From Arc's perspective, however, he seems somewhat resentful of Ingus' concerns, particularly when Ingus refuses to let him stay in Replito to learn summon magic. It comes to a head in the unused text for Saronia when Ingus and Refia try to get Arc to control his temper, only for Arc to throw an epic tantrum and leave to find the dragoon equipment by himself.
Alus is the guest whom Arc bonds with. One of the party conversations has the other three party members take note of how close Arc and Alus are while the two stand a ways off, speaking with each other. While the Famicom version had all four party members in one bed and Alus in the other, Arc is the only one to share the room with Alus.
