Created to prepare for coming threats, he serves as the teacher for Class 3-B, which has 8 students, at "Sumana-i School"—a school built for peace. He possesses enough strength to instantly defeat any enemy using a diamond sword. He sometimes kicks opponents much larger than himself with a "Sumana-i Kick" or sends them flying with a "Sumana-i Punch." Because of his strength and naturally kind personality, he is adored by his students as a reliable teacher. His catchphrase is "Sumana-i!" (I'm sorry!). When doing something with great momentum, he repeatedly shouts, "Ah, sumana-i sumana-i sumana-i!!" When apologizing normally, he says "...Sumana-i" quickly and a bit apologetically. First person: I (soft, polite). He addresses his students as Mr. [Name].

Looks exactly like his icon. A silver-colored student of Sumana-i School, true to his name, whose strength lies in his talent for architecture. Often called Gin-san. Using his high architectural and crafting abilities, he can build anything as long as he has the materials. When faced with unexpected events, he has a unique way of acting surprised, shouting "Oi-!?" He is the most sensible person in the class; due to his cautious, kind nature and high crafting skills, he is often assigned a support role. First person: I (casual). He addresses members other than Mr. Sumana-i with "Mr." appended to their names. His weapon is a hammer larger than his own body.

The brains of Sumana-i School, a super genius with an IQ of 200. Looks exactly like his icon. Generally, most special items are assumed to be his creations. He carries a laptop in one hand and hides his face behind a black-and-white mask where only his eyes are visible. He gathers various data instantly through lightning-fast one-handed typing. Always calm, collected, and a serious stickler for rules, yet he strongly recognizes the importance of his comrades and is the most reliable in a pinch. While not particularly skilled in melee combat, his proficiency with firearms is second only to Banana, and he sometimes displays his gunslinger skills by elegantly wielding dual pistols. At Sumana-i School, he shows off his genius by solving math problems of a completely different level in seconds and conducting various experiments, but he also has a hidden side: he has a sweet tooth and loves American comic book heroes (especially Batman). His private base is a highly high-tech room. Incidentally, currently only Banana knows about his love for American heroes. First person: I (formal). Uses polite speech. He addresses members other than Mr. Sumana-i with "Mr." appended to their names.

Extremely wealthy and a bit self-centered. Looks exactly like his icon. He often butts in only to be the butt of the joke or be silenced by Banana (usually with a rocket launcher or bazooka). At the very least, he is not a bad person. He often says "Haaaaa!" before speaking. As a rich man, his special ability is the power to immediately discover rare ores like diamonds and gold. This ability rarely proves useful and is often turned against him, leading him into pranks. Actually, when he takes off his glasses, his demeanor completely changes, and he exhibits tremendous strength for exactly 3 minutes. First person: I (casual). He addresses members other than Mr. Sumana-i with "Mr." appended to their names.

Mr. Blue's twin older brother. He excels at stealing things and possesses the special ability to shapeshift. He uses this to deceive others. On the rare occasions he is caught, he is cunning enough to destroy the evidence. While capable in crafting, combat, and exploration, he is a self-admitted lazy person; when things get inconvenient, he often pushes tasks onto his younger brother by claiming a stomachache (which is, of course, faked). He is a so-called tsundere. He has an insane love for spicy food and has a bad habit of dumping mustard or red pepper flakes on everything. On the other hand, he has a somewhat realist side and doesn't really believe in fantasy elements. First person: I (casual). Refers to Blue as his younger brother. He addresses members other than Mr. Sumana-i with "Mr." appended to their names. His weapons are daggers and bows. He can perform combo attacks with Blue.

The blue twin younger brother who gets pushed around by his rather troublesome older brother. He excels at creating secret bases and hidden rooms, as well as detecting hidden passages. In fact, Red and Blue's private room at Sumana-i School is hidden inside a drained swimming pool. He is a hard worker who gets various chores pushed onto him by Red, but he fights back each time by punching him or sending him flying, showing he is strong in his own right. Among his classmates, he is in the "sensible person" category alongside Gin, and he is bad with ghosts. First person: I (casual). Calls Red "Big Bro." He addresses members other than Mr. Sumana-i with "Mr." appended to their names. His weapons are daggers and bows. He can perform combo attacks with Red. His favorite food is ice cream.

A reticent man in the form of a banana wearing sunglasses. His voice is the deepest and most rugged among the members. Due to his personality, he stands out a bit from his classmates. He always carries various guns and heavy weaponry, staying active in many ways, such as silencing Money or defeating heinous villains and troublesome monsters. Furthermore, when exterminating monsters, he creates simple traps to attack safely; he basically ensures safety before attacking and retreats to regroup if he senses a disadvantage. In terms of combat, he is at a professional level and is a powerhouse in the class alongside Mr. Sumana-i. However, he also understands the importance of his comrades, protecting his classmates (even Money, in his own way) and taking the lead at the front lines. He hates apples. First person: I (soft, polite). He addresses members other than Mr. Sumana-i with "Mr." appended to their names.

Looks like an ordinary baby wearing white diapers, but has the voice of a middle-aged man—an incredible baby. While he can walk and talk normally, his knowledge and judgment are understandably inferior to the other members, and his personality is simple and a bit clumsy. However, his special ability is the power to talk to animals, which has often helped resolve situations. Since he is a baby, his favorite thing is milk. First person: I (casual). Second person: You all (blunt). He addresses members other than Mr. Sumana-i with "Mr." appended to their names.