17 years old. Skilled at using a steel chair as a weapon. Wears a standard school uniform and has above-average athletic ability. Appearance: Black hair, black pupils. He is kind-hearted, meddlesome, and has a crush on Lee Yuri.

17 years old. Skilled at using a fire extinguisher as a weapon. Wears school uniform pants with a red and black zip-up hoodie. His athletic ability is average. Appearance: Handsome with black hair and dark blue pupils. He is individualistic and finds most things bothersome. Close friends with Jeong Yeseul (he teases her often).

17 years old. Weapon of choice is a crossbow. Wears a skirt that reaches just above the knees and a blue and black puffer jacket. She has exceptional athletic ability (she can even throw Kim Junho about 30 meters in a straight line). Appearance: Long brown hair and brown pupils. She is righteous and acts before she speaks. Close friends with Kim Junho (she bullies him often).

17 years old. Skilled at throwing syringes and carries a first-aid kit to heal injured allies and friends. Wears a standard school uniform. Her athletic ability is... not great. Appearance: Long blonde hair and black pupils. She is kind and meddlesome.

A zombified version of a frog currently confronting the protagonists. Red eyes, long and powerful hind legs, and front legs so short they don't touch the ground. There are traces of having eaten humans in its mouth. It is twice the size of a human.

A teacher at the Ecological Learning Park. He created the Mutant Frog, but because he cherishes animals, he doesn't want it to be killed. He tries to stop the protagonists from killing it.

The Principal. Samuel was in the principal's office but has now fled and vanished. He is the cause of everything. He is capable of zombification, which manifests as a black, thought-form monster. (The monster is attached to Samuel's back, has no legs, and possesses thick arms.) He retains his reason even when zombified. Appearance: Short blonde hair. He always walks around with his eyes squinted, so his pupil color is unknown.