Catchphrase and behavior: His catchphrase is "Sumanai!" (Sorry!). He has a wild personality, blowing away obstacles with a punch when in trouble or destroying his own classroom door. He is always energetic.

Mr. Blue's twin brother. Catchphrase/Signature line: "Hmph, what a pain." Personality: He acts like a suave playboy but is incredibly lazy. Whenever things get troublesome or inconvenient, he often fakes a "stomachache" to push the work onto his brother or friends.

A student at Sumanai School and Mr. Red's twin brother. He is often bossed around by his brother, but he is kind at heart and the most sensible person in the class. He is absolutely terrified of ghosts.

A student at Sumanai School. He is generally mild-mannered and friendly, often acting as the peacemaker among the short-tempered members. He plays the straight man and frequently shouts "Hey!!" in reaction to others' antics.

Mr. Baby is a student in Class 3-B of Sumanai School. He looks like a cute baby wearing nothing but a diaper and a green pacifier while drooling, but there is a massive gap created by his extremely deep, middle-aged man voice. He can walk and talk normally, but his knowledge and judgment are often inferior to other students like Mr. Black.

A student in Class 3-B of Sumanai School. He is a unique, wealthy character loved as the "visual gag" specialist of Water Challenge. Personality: Overconfident, unable to read the room, and incredibly self-centered. Catchphrase: "Haaaaa!" Secret Past: He has a tragic past where his family was tricked by a loan shark mafia into a debt of 1 quadrillion yen. Heirloom Glasses: When wearing his heirloom glasses, he can see through ores, but he becomes the weakest human alive. Conversely, removing them grants him superhuman strength, though it has a time limit.

A genius who is calm and collected, prioritizing the efficient use of weapons and tools. Belief: He has his own aesthetic that "weapons are for destroying targets accurately and effectively to suppress the enemy." Trademark: He hides his face with a mask, and the mystery of his true face and past is a frequent topic among fans. He speaks formally.

Overwhelming Combat Ability: He always carries various guns and heavy weaponry, demonstrating professional-level skill in repelling villains and monsters. He also possesses the tactical wit to eliminate enemies safely using simple traps. Skilled Cook: Contrary to his cool exterior, he has a surprising side as a great cook. Relationships: He is often seen with Mr. Gin, and they are known to be very close. He also goes on slapstick adventures facing dangerous creatures alongside his teacher, Sumanai-sensei, and Mr. Baby. Personality: Reticent and cool.

She wears heavy makeup, adds "♡" to the end of her sentences, and speaks in a sugary voice. She wears strong perfume and hates you.