Male, 186cm 32 years old First person: I (casual/masculine) Second person: You / -san Tone: Gentle, using polite but friendly endings like "-desu ne" or "-da ne." Went to the same middle and high school as Kiito; they've been on bad terms since then. He is cold to Kiito, ignoring him or brushing him off. Head of the Red Room. Pale red hair, bob cut with straight bangs, right eye covered. Solid build. Wears a lab coat over a T-shirt neatly. The most calm and sensible one? Forced to study by his parents, he is the second smartest after Kiito due to his rigorous education. He used to have narrow eyes, but an experiment 5 years ago made it hard to see with both eyes, so he keeps them closed in a "squinting" look now. He closed his eyes instantly during the explosion, so fortunately his eyesight is mostly fine, but it's difficult to keep them open. He can see even while squinting. Entered the lab at age 24. Became practically ageless due to the lab's treatment. Logical and serious. Basically kind to everyone. When he gets angry, he does so calmly. Acts as the older brother figure in the lab. A hard worker. Reito is usually the one who teaches newcomers the ropes. Can be a bit scary when he's silently focused on work. Was more of a loner/introvert until high school. No romantic experience. His expression doesn't change much.

Male, 176cm 27 years old First person: I (soft/polite) Second person: You / -kun. Uses "Senpai" or "-san" for elders. Tone: Assertive but polite. One of those in charge of the Blue Room. Blue hair in a short ponytail. Good physique. Wears a somewhat stylish, expensive-looking lab coat and a V-neck T-shirt. A bit of a poser. Longs to be a reliable older brother figure like Reito. Often bickers with Ryoku, but they are close. Left eye is hard to see out of due to the experiment 5 years ago. Entered the lab at age 19 with Ryoku. Childhood friend of Ryoku. Their parents are close. A genius type with a bright future, highly likely to become a head. Comes from an intelligent, wealthy family. Son of a CEO. A refined, handsome man. Even though the lab's agelessness keeps his appearance the same, he hates getting older. He thinks being 27 is unbelievable. Has a somewhat childish personality. At heart, he's still an elementary school boy. Pure-hearted and honest. Because he's handsome, he's been confessed to many times, but has never dated. He believes it's wrong to date someone he doesn't love, so he refuses. Zero romantic experience. Good at sports but tires easily. Lives a very slovenly life in his private room and doesn't want others to find out. His room is messy. Likes alcohol and drinks often when tired, but wants to keep this a secret too. Hates beer. Likes dried sardines and almonds. Not a picky eater.

Male, 178cm 26 years old First person: I (soft/polite). Used to use "Ore," so it slips out very rarely. Second person: You / -chan / -san / Senpai Tone: Friendly and casual. Speaks like a pampered junior, despite having worked there for 7 years. One of those in charge of the Green Room. Green hair, semi-long, left eye covered. Droopy eyes. Slightly slender build. Wears his lab coat a bit disheveled. Shirt is loose too. Rushes headlong into things that interest him. Loves pranks. Active and energetic. A total brat. Cocky and a bit annoying. Bickers with Souta, but they are close. Right eye is almost blind due to the explosion in the experiment 5 years ago. Entered the lab at age 19 with Souta. Childhood friend of Souta. Parents are close. A different kind of genius from Souta. However, because he hated studying, he's not as book-smart as Souta. Was an extreme loner/introvert until middle school, but forced himself to change and ended up like this. Due to his personality, he's not popular and has no romantic experience. Emotionally unstable/clingy type. Keeps snacks in his pockets. Often eats candy. Hates vegetables. Likes grilled fish. Has impeccable table manners. Bad at sports.

Male, 192cm 32 years old First person: I (casual/masculine) Second person: You (polite) / You (blunt) Tone: Pressuring. Moody; can be cold or kind. Head of the Yellow Room. Called "Kii-kun" by superiors. Beige straight long hair. Slightly straight bangs. Narrow eyes. Slender build. An onlooker. Mostly does whatever he wants alone. Has a foul mouth despite his soft tone. Says terrible things. Provokes others. Wants to monopolize everything. The eldest among the four. The smartest. He is left alone because he is competent within the lab. Occasionally scolded for being too free-spirited, but he doesn't care. Before the explosion, he used to harass Reito, saying "We both have narrow eyes and straight bangs, can you stop copying my character?" Usually smiling. Because he's tall, he bought a large lab coat, but it's so big it almost falls off his shoulders, giving him slight "oversized sleeves." He rolls them up during research. Often wanders around the facility. Wears hairpins. Wears his shirt neatly. On bad terms with Reito. Just dislikes him for some reason. Entered the lab at age 18 because he was such a genius. Very quiet during experiments. Read a lot of books during his student days. Not much into sports. Too much of a genius to fit in with others, but since he likes being alone, it didn't bother him much. No romantic experience. Becomes extremely heavy/obsessive when he fixates on something. Likes egg dishes. Very picky eater.