A lot of characters in Errant have swords. My main aim was fun and visual appeal rather than accuracy, because like... if somebody can seriously be content with magic that makes your hair turn blue and cut things with your aura or throw cars, but they draw the line at swords that aren't perfectly accurate... they have weirdly patchy suspension of disbelief. 
I have some training in iaido myself, and I know the rudiments of fencing, but I wouldn't call myself an expert.
So... the characters' swords, here we go:
Rekki in the prologue uses a nice simple arming sword. It's on the small side because she's a small lass, but I'll still call it an arming sword rather than a short sword. It's the archetypal "knight sword" (sometimes mislabelled as a "longsword") because Rekki's whole deal is she really wants to be a knight.
After breaking her sword due to gaining super strength, she gets that ridiculous big rectangle, which I can only call an "anime greatsword" or a "buster sword". It bears no resemblance to any real sword ever. Rekki has named this sword "Thor's Chisel" but everyone else calls it "Trash Smasher" because it's a piece of junk. Trash Smasher is partially designed that way so it doesn't break when she hits big monsters with it and can hold a lot of magical energy (because Rekki's magic is all red wavelengths and doesn't transmit well over distance so her sword draw attacks are very energy inefficient) and partially for show, because Rekki's a bit of a show off. The blunt end is to show that she only fights demons (which can only be killed by hacking parts off) and not humans, so she has no need for stabbing. Mostly it's a silly big sword for fun that represents Rekki's blunt and impetuous personality.
Subo Talwar wields.... the Talwar family talwar! Did you know Talwar is an actual south asian name? It's pretty badass being called "Mister Sword" right? Anyway, the Talwar is a traditional south asian sword, and like most curved blades, it's very effective for draw attacks, both the real life kind and the magical kind used in Errant. Subo doesn't really like to fight though...
Sarin Aoki in the prologue wields a rapier. She's a careful combatant who likes to keep the enemy at arm's length, she's meticulous, precise and light on her feet, and she has a tendency to hesitate waiting for the perfect moment.
After the prologue we've only seen her on covers and artwork, but she has a fancy looking katana the saya (sheath) in particular is more ornate than most. I can't talk much about this weapon without spoilers, but katana in general are good for drawing attacks but poor for parrying. There are a lot of myths about katana, for example that they're lighter than western swords (they're not) that gives them an almost magical status.
Urien in the prologue and then after the timeskip his sibling Jules wield what would be best described as a ninjatou without a guard. It's not really a "real sword" because there's no evidence ninjatou were ever actually used in history. Urien even wears his on his back which... well, any person who knows about swords knows that you can't really sheathe a sword on your back like that... (sorry, Geralt) but the thing is it looks cool, and Urien is all about looking cool. I wanted their swords to have an understated quality that shows they're both kinda sneaky or elusive types. Neither of them has drawn one of these on-panel yet. 
After the prologue, Urien wields Excalibur! I designed Excalibur to look Fantastical over anything else. It had to be unmistakeable because it's the main plot macguffin, and I also wanted something that'd look iconic when stuck in the ground so it has this distinctive design with lots of chevron-like shapes that point up and down. It's basically a Fantasy greatsword, not designed to look practical at all.
In summary, I know a reasonable amount about swords, so the reason the swords are very silly and completely unrealistic in Errant is because it fits with the silly, overblown anime-esque aesthetic of a comic where a lady in chest-high sailor pants with postbox red hair punches giant demons in studded leather chaps.
