Thanks to EternalSunset0 for the idea about the glossary.
Character profiles are taken from my own notes with some modifications here and there. More will be added as the story goes (assuming I do resume writing).
Might contain discrepancies with how they're actually portrayed in the story. Think of it as a rough, very basic description with a bit of color guide.
No images for now because I can't draw myself, there are only rough sketches(?) for a handful of characters, and I'm not sure which one to pick.
Please imagine/pretend the characters are drawn by Komori Kei or Amasaka Takashi for MAXIMUM HAPPINESS (they are obviously not voiced by professional seiyuu, as well).

ADDENDUM: Added AI art, for fun.

CV: Eri Kitamura
The flagship heroine. 2nd-year. Blonde long hair with small 'drills'/slight curls. Blue eyes. Daughter of a prestigious noble family, her calm, refined, and honorable demeanor inspires admiration to those around her. On the flip side, she becomes passionate when it comes to dueling, and fights aggressively more like a warrior than a knight. The current student council president and the academy's only S-ranker. Best friends with Chelsea.
Weapon: Great spear "Badb"
Birthday: October 31st (Winter's Eve)
Hometown: York, England
Image song: Winterfylleth – The Fields of Reckoning
Height: around 167 cm
3 sizes: 94-60-89

CV: Lynn
1st-year. Dark blue, high ponytail. Green eyes. Sigulf's friendly rival of sorts. A strong girl with a personality to match. Quite hot-blooded, and sometimes likes to be smug when she feels she one-upped Sigulf. Eats a lot because she inevitably burns a lot of energy, yet somehow never gained weight. A commoner, thus explains her preference towards munchy box.
Weapon: Highland claymore "Braveheart"
Birthday: June 24th (End of Battle of Bannockburn)
Hometown: Inverness, Scotland
Image song: Saor – Hearth
Height: around 168 cm
3 sizes: 85-57-84

CV: Ai Kayano
2nd-year. Shoulder length, straight brown hair. Blue eyes. The current vice-president. While she is a caring older sister type, she can also be quite the tease, or sometimes spouting some suggestive lines (though she's still able to get flustered). A rich city girl who likes shopping on her free time, yet a formidable fighter nonetheless. Best friends with Celina as they have known each other for a long time.
Weapon: Sword & round shield "Stamford"
Birthday: September 25th (Battle of Stamford Bridge)
Hometown: London, England
Height: around 166 cm
3 sizes: 89-60-85

CV: Atsuko Tanaka
A woman in her 30s. Wavy brown long hair with a slight red-tint. Blue eyes. The Academy's principal. A powerful Duelist during her pro days as well as a successful businesswoman. Her cool, almost cold demeanor and her tenacity on building her own 'empire' earned her the nickname Steel Lady. ...which is really jarring as currently she took a liking towards Sigulf and dangerously teases him, although she is still as strong as ever and didn't neglect her duties either.
Weapon: Mechanical fighting gloves "Blade Breaker"
Birthday: September 4th (Crowning of Aethelstan)
Hometown: Windsor, England
Image song: Wodensthrone – Heófungtíd
Height: around 170 cm
3 sizes: 100-60-95

CV: Shizuka Ito
Sigulf's master and legal guardian. Auburn brown/copper-red slightly shaggy long hair. Blue eyes. A carefree woman who loves to tease his disciple/adopted son, and is quite the drinker. She was a highly promising talent, enough to warrant the nickname "North Sea's Finest", but a terrible accident put an end to it, cutting her career very early. Eliot and Melanie's old classmate.
Weapon: Twin short-bearded axes "As-hnaeigr" (a.k.a. Aesir's Fall)
Birthday: Unknown; picked January 5th (First Constitution of Iceland)
Hometown: Unknown; same with Sigulf
Image song: Kontinuum – Lightbearer
Height: around 170 cm
3 sizes: 90-58-88

CV: Yoshitsugu Matsuoka
1st-year. Black hair. Dark brown eyes. Describes himself as an average high-schooler. ...this is despite his above average looks, his tendency to jump in and help whoever in need, or how he is well-trained in fighting, both traditionally and for Dueling. Sometimes blurts things bluntly. No one is sure whether he is oblivious towards girls or is aware but just too embarrassed.
Weapon: Mechanical longsword "Sky Fencer"
Birthday: September 16th (Allegedly the most common birthday)
Hometown: Saitama, Japan
Height: around 172 cm

CV: Shizuka Ishigami
1st-year. Bright pink twintails. Dark red eyes. Daughter of a wealthy family, which possibly explains why she can't cook. Often short-tempered, especially when she is dealing with a certain someone. On the other hand, she is serious and hard-working when it comes to any task at hand, as if to prove herself. A textbook tsundere.
Weapon: Rapier "Eos"
Birthday: September 12th (End of Greek War for Independence)
Hometown: Athens, Greece
Height: around 158 cm
3 sizes: 79-55-82

CV: Miyuki Sawashiro
1st-year. Long wavy red hair, with her bangs over left eye. Amber eyes. Daughter of a noble family, in spite of her rather provocative looks and personality. Quite the shameless seductress and is not above using her beauty, but she doesn't flirt with everyone. Which makes her prowess in Dueling surprising. Seems like her rivalry with Eurypha didn't came from genuine malice, at least from her side.
Weapon: Scythe "Venus"
Birthday: October 28th (Formation of RCD Espanyol)
Hometown: Barcelona, Spain
Height: around 169 cm
3 sizes: 94-59-91

CV: Inori Minase
1st-year. Short white hair. Gray eyes. Looks like the typical emotionless girl, but is actually rough and slightly violent. Kind of grumpy and gets easily annoyed by most things around her. Likes beer despite obviously below age. Failing that, she'll opt for coffee or energy drink. Unlike her two rivals, she came from a normal family. Back then, some people joked that her name is short for ill-mannered, which doesn't end well for them.
Weapon: Twin military knives "Tuonetar"
Birthday: December 6th (Finnish Independence Day)
Hometown: Espoo, Finland
Image song: Mors Principium Est – Dead Winds of Hope
Height: around 165 cm
3 sizes: 76-54-74

CV: Soma Saito
1st-year. Long, black, 'hime cut'-ish hair, tied in a low ponytail. Dark brown eyes. In contrast to his soft features and speaking mannerism, he's probably the most perverted of the bunch. His family descended from merchants who split off from a warrior clan, probably explaining his rather laid back nature towards fighting and preference for ogling girls instead. Still, he has the skills and can put actual effort if he has to. Could be considered Sigulf's sidekick and likes to mess with him, something Chelsea really appreciates for some reason.
Weapon: Uchigatana "Susanowo"
Birthday: August 1st (Hikawa Shrine Reisai)
Hometown: Yokohama, Kanagawa, Japan
Image song: Onmyouza – Susanoo
Height: around 168 cm

CV: Ryota Ohsaka
1st-year. Spiky orange hair. Hazel eyes. Grandson of a newly-rich entrepreneur. Due to the "American frontier spirit" (or something), he got enrolled into Atlantic Academy. Loud, brash, and perverted, though still a good kid at heart. Helps that he knows how to throw down too. Definitely Minato's sidekick.
Weapon: Huge steampunk gauntlets "The Pioneer"
Birthday: February 2nd (Dallas granted its town charter)
Hometown: Dallas, Texas, U.S.A.
Height: around 180 cm

CV: Nobuhiko Okamoto
2nd-year. Long black hair. Brown eyes. Looks grim, but is actually a pretty chill guy and doesn't talk much. Everytime his weapon is summoned, however, his personality switches to a near berserk state. Plays viking black metal on the side, and bonds with Sigulf over the Nordic heritage.
Weapon: Huge claw-gauntlets "Nidhoggr"
Birthday: February 28th (Release of Enslaved's Vikingligr Veldi)
Hometown: Bergen, Norway
Image song: Enslaved – Midgards eldar
Height: around 178 cm

CV: Kanae Ito
2nd-year. Very wavy, light blonde long hair. Light blue eyes. Works as a part-time model and likes to share some fashion knowledge with Chelsea. Mypace, maybe a bit airheaded, and tends to be unmotivated in anything else besides fashion/modeling. Still not half bad at dueling, and somehow good with observation and covert information gathering despite all that.
Weapon: Chained-harpoon 'Vete-ema'
Birthday: February 24th (Estonian Independence Day)
Hometown: Tallinn, Estonia
Height: around 166 cm
Image song: Metsatöll – Kahjakaldad
3 sizes: 84-56-83

CV: Ryohei Kimura
Short-almost-medium length blonde hair. Green eyes. Sigulf's homeroom teacher/instructor, and definitely a bit younger than the norm. Looks a bit strict, but at times showed that he's not as straight-laced. Old classmates with Vigdis and Melanie, and was the self-proclaimed rival to the former. Used to be more competitive before Vigdis' accident.
Weapon: La Tène longsword "Anvalos"
Birthday: February 12th (Oaths of Strasbourg)
Hometown: Strasbourg, France
Height: around 179 cm

CV: Yuu Asakawa
Dark purple long hair, styled in an up-do. Green eyes. Wears thin glasses. The (token hot) school nurse. Sometimes she teases Sigulf, though in her case it's more for the giggles. Old classmates with Vigdis and Eliot, and the midway balance between the two. Not that it stopped her from joining Vigdis whenever they decided to mess with him.
Weapon: Metal staff "Nehalennia"
Birthday: September 14th (End of Siege of Den Bosch)
Hometown: Den Bosch, Netherlands
Height: around 167 cm
3 sizes: 87-57-85

CV: Maaya Sakamoto
1st-year B-class. Blonde, low braided hair. Green eyes. Arthfael's Knight Circle member, and is really loyal to him (possibly more?). Her being a devout Christian makes an amusing contrast with the other Pagan or non-religious students.
Weapon: Energy-flagged spear "La Pucelle"
Birthday: May 16th
Hometown: Domremy, France
Height: around 163 cm
3 sizes: 82-59-83

CV: Nobunaga Shimazaki
1st-year B-class. Icy silver long hair. Icy blue eyes. Often mistaken as a knight, which is actually his pet peeve, as he dislikes them and is actually a warrior. Also often assumed to be cold due to his looks, but prone to extra theatrics. Tried to gain Sigulf's alliance(?) based on the Nordic/Germanic connection. The 'good looking but doesn't think far ahead' type of guy.
Weapon: Zweihander "Grimm"
Birthday: September 9th
Hometown: Gelsenkirchen, Germany
Height: around 178 cm

CV: Marina Inoue
1st-year B-class. Medium length gray hair. Brown eyes. Wears a long scarf. Has a slightly rough mannerism and speech pattern, despite her stereotypical shinobi-ish look. Tends to be more cool-headed than Siegward and often get exasperated at his antics, though she sticks with him nonetheless.
Weapon: Omi-yari "Oni-Hanzou"
Birthday: June 22nd
Hometown: Iga, Mie, Japan
Height: around 164 cm
3 sizes: 81-54-74

CV: Taku Yashiro
2nd-year. Dark brown hair and eyes. Charismatic and gentlemanly, he is the current Ace of the Pacific Academy. Rumors said he has a merciless, almost murderous side if pushed too far (especially in duels), but no one has been able to confirm it. Being Jack's designated mentor, his very patient way of dealing with him left others doubting the aforementioned rumors, but even then they realized that the younger boy never even raised a hand against him (though he often disagrees verbally nonetheless).
Weapon: Longsword "Astral Phoenix"
Birthday: May 21st (Golden Star)
Hometown: Kagoshima, Japan
Height: around 172 cm

CV: Makoto Furukawa
1st-year. Blonde spiky hair (possibly a mullet/faux-hawk) with a long tail. "Dark" skinned due to being sunburnt/tanned. An orphan born with superb physical capabilities, his innate talent made him grew into an arrogant young man, condescendingly thought everyone inferior is a worthless trash. That is, until he met and got scouted by Kouji after spending his early teenage years in illegal duel rings. He did grew a begrudging respect towards him, and to the rest of the special team on a lesser extent.
Weapon: Cavalry saber "The Revolution"
Birthday: April 19th (US Revolution War)
Hometown: Yuma, Arizona, U.S.A.
Height: around 179 cm

CV: Houko Kuwashima
1st-year. Straight and sharp medium-length black hair, with the front/sides longer than the back. Dark brown eyes. Quite serious and very competitive when it comes to duels, otherwise is friendly outside it. Despite ranked 2nd among the freshmen, she is often considered as the unofficial leader of the special team due to Jack's bad behavior, and always trains hard in hopes of surpassing him. Wears a customized sleeveless uniform and trousers instead of the usual skirt. Seemingly doesn't really care about romance or the such.
Weapon: Wolf teeth mace "Xuan Nu"
Birthday: May 13th
Hometown: Yangzhou, China
Height: around 171 cm
3 sizes: 83-56-76

CV: Chinatsu Akasaki
1st-year. Long brown hair. Brown eyes. Her bangs are a bit too long, so sometimes she has to wear a headband. Serious, diligent and likes to train, giving an impression that she's even more passionate than her teammate Mei. Looks like a normal modern high school girl, but is actually quite old-fashioned, reflected by how she ends her sentences with '-de gozaru' or addresing others with '-dono'. Apparently distantly related to Yuu.
Weapon: Tachi "Rasetsu"
Birthday: October 1st (Kendo kari)
Hometown: Asakusa, Tokyo, Japan
Height: around 166 cm
3 sizes: 80-55-75

CV: Mikako Komatsu
1st-year. Shoulder length white/silver hair. Baby blue eyes. A meek and unassuming student. Seems to be lacking in confidence and/or slightly anxious, but will not back down when it comes to the push. Likes computer programming on free time.
Weapon: Kinzhal "Siebog"
Birthday: February 4th (Nizhny founding date)
Hometown: Nizhny Novgorod, Russia
Height: around 161 cm

CV: Mamoru Miyano
1st-year. Slightly wavy black hair. Dark brown eyes. Lighter skinned. A quiet, almost docile boy, even more than Lindorm. For some reason prefers to emote using simple body gestures. But when it comes to duels, he somehow became loud and hot-blooded. No one really knows what's on his mind, but otherwise is a good kid.
Weapon: Firangi "Garuda"
Birthday: November 1st (Official Kannada name implementation)
Hometown: Bangalore, India
Height: around 166 cm