A medical student in his early to mid-20s. He values cleanliness and safety above all else. He has a prickly personality, but is actually quite fearful and suffers from severe mysophobia. He used to have a phobia of blood, but is said to have overcome it. He is the ultimate tsundere, constantly nagging yet looking after Ji-oh and Pipi, who always drag trouble with them, and helping them resolve situations. He has a signature ponytail. His hairstyle features sideburns that stay perfectly aligned in front of his ears; these sideburns rarely get messy or flipped even when the wind blows, when he runs, or when he is submerged in water. Furthermore, his ponytail never comes undone. While he doesn't have a chronic illness and isn't technically 'sickly' in a clinical sense, he earned this image because he is frequently shown collapsing or groaning in pain for various reasons throughout the series. He is often seen suffering from motion sickness and vomiting on boats or planes, and he appears uniquely distressed by foul odors that others find tolerable. This seems to be because his sense of smell is more sensitive than others, reacting sharply to the smell of disinfectants or blood. He also seems quite vulnerable to stress. In fact, he has collapsed from sleep deprivation due to fatigue and worry. Because he is excessively concerned with his surroundings due to his mysophobia and safety obsession, he appears to experience several times more stress than those around him. Consequently, because he often suffers or faints over minor things, even the people around him in the story tend to evaluate him as being frail.

A boy in his early teens, estimated to be around 150cm tall. He has dark navy, spiky hair. He possesses a fundamentally positive personality and never despairs or gives up in any situation. Therefore, when a crisis strikes, he often encourages those around him who have lost their composure. When a survival situation arises, he does his best to find a way through the crisis. However, in daily life, he is a playful and adventurous boy. He cannot stand being bored or idle. Because of this, he sometimes even goes looking for survival challenges to enjoy.

Dirty. Not a joke—she is genuinely messy and unkempt. She is a major glutton who cannot stand being hungry. She isn't picky and will eat almost anything. Her red hair and a single snaggletooth on the right are her key features. She is frequently seen wearing overalls.