A member of the Ares Class with a translucent silver ponytail and sparkling amethyst (purple) eyes. A healthy, beautiful girl whose expressions change vividly. A direct descendant of the Vulcan family, which originated from Vulcan Heavy Industries—a company that once strove for human reconstruction. As a wielder of the Artifact-class Fenrir, Iris should have originally been raised in the academy's highest tier, the "Zeus Class," as its top student on the safe upper decks. Despite being a High Razer (Great Machine Beast User) with overwhelming combat sense, she is the academy's idol and mood maker with no air of pretension. Because she talks to everyone in a friendly manner, she is adored as "Iris-chan" not only by the elite Ares Class but also by the students of the modest Tartarus Class. While invincible in combat, she is quite careless in her daily life. She has trouble sitting still and often dozes off during classroom lectures. Above all, she is a huge glutton. She is constantly hungry and always seems to be eating something with great relish. Her partner is the Artifact-class machine beast "Fenrir." A large, wolf-type machine beast covered in ultra-hard, silver-colored streamlined armor. High-output Prometheum energy glows with a gentle blue light from its eyes and joint slits. It is equipped with a variable "High-Output Photon Booster" on its back. Much like its master Iris, it is generally friendly and intelligent (with a side that resembles a large dog), but it shows no mercy when baring its fangs at enemies.

A beautiful girl in the Zeus Class with elegant blonde ringlets, pink eyes, and a custom-made uniform as elegant as a dress in silver and purple. She always carries a high-tech folding fan that can deploy a hologram keyboard. As the daughter of the Arclight family, she boasts the top grades even within the Zeus Class. As Iris's best friend, she looks out for her in various ways. Though she has a somewhat unapproachable and haughty attitude, she is a girl with deep kindness and the pride of a technician. Her partner is the Artifact-class parrot-type machine beast "Toto." A sleek, palm-sized parrot-type machine beast. Its entire body is covered in mirror-finish alloy, and precise fiber-optic lines emit purple light from the gaps in its feathers. Its round eyes are ultra-high-performance lenses that project holograms. It possesses extremely high intelligence and speaks human language fluently (in a slightly cheeky mechanical voice). It calls its master Serena "Milady" and makes it a daily routine to groom her ringlet hair. Toto has a portion of the Master Management Privilege Codes (Root Access) built into its body. Therefore, it can hijack the actions of nearby wild machine beasts by sending fake commands (Fake Codes) or instantaneously control all infrastructure of the academy's mobile fortress.

A petite girl in the Hephaestus Class with oversized work goggles on her head and oil-stained overalls tied at her waist, sporting a bun hairstyle. Her pockets are always stuffed with wrenches and suspicious measuring instruments. Her resonance volume is extremely low, and her talent as a Razer (Machine Beast User) is absolute zero. However, she is a genius in "Technical Development and Structural Analysis" that more than compensates for it. The fact that she is entrusted with the complex custom maintenance of Iris's Fenrir and Rei's Twins in her teens is due to her staggering technical prowess. Her greatest flaw is that her love for machine beasts is so deep that her sense of fear is completely paralyzed. If she decides she wants to "collect raw data on a Vulture-class!", she will secretly sneak into the front lines with nothing but a helmet. Even when a wild machine beast approaches with a roar, she is a regular at the disciplinary office because she's too busy happily filming it. Her name is a pseudonym taken from an electrical engineer from before the Great Meltdown.

A large young man in the Ares Class with spiky black hair and scars on his cheeks that tell of many fierce battles. He rolls up his uniform sleeves wildly and wears a choker made of machine beast fangs around his neck. A hot-blooded muscle-head who acts before he thinks. However, on the battlefield, he is a combat genius who can sense the presence of machine beasts and the tide of battle instinctively. He also has a kind side, treating the protagonist—a Lost One—in a friendly manner. Furthermore, he has a more considerate personality than his appearance suggests, properly addressing superiors like Iris and Serena as "Senpai." His partners are the twin Vulture-class leopard-type machine beasts, "The Twins." "Left Ein" and "Right Zwei" are sibling units born from the same core code. Their tactic (Combination): Through Rei's mental multi-threading, they specialize in perfect time-lag coordination (Chain Attacks) where one unit draws the enemy's attention while the other leaps from a blind spot to finish them off.

A girl in the Ares Class. She has sleepy, half-open red eyes with a scornful look. Her hair is long, unkempt black hair that glows with a slight purple tint. To hide her petite frame, she always wears an oversized white coat two sizes too big, with sleeves covering her hands. Despite being a regular first-year, she commands a Titan-class and holds the title of "High Razer," making her a mysterious girl held in high regard at the academy. She is always spacing out, speaks extremely little, and spends most of her day sleeping on top of Roku's shell. Her partner is the Titan-class tortoise-type machine beast "Roku." A tortoise-type machine beast with a body made of ultra-high-density black iron armor and a built-in Prometheum barrier generator. Despite being a Titan-class (large scale), it has a function to compress its own mass and volume to the size of a human's back when not in combat. When battle begins, Roku performs a "Mass Release" into its original Titan-class giant form.