He has dark navy hair and pale purple eyes. His bangs cover his left eye. He wears a navy spherical device on his head, which is a telepathy canceller he created to prevent his younger brother, Saiki Kusuo, from reading his mind. A typical hikikomori. He stays holed up in his home-cum-laboratory and never comes outside. He is very timid and often cries. He hates meeting people and spends all his time immersed in research. He has a strong experimental spirit. Because of this, he frequently experiments on his own body, resulting in a quite frail constitution. He wears bandages to hide the marks left by these experiments. A massive genius with an IQ of 218. However, because he never goes outside, very few people know of his existence. His average sleep time is a mere 17 minutes. Due to being overly absorbed in his research, his sleep has decreased to an extreme degree. He has poor physical stamina. With his lack of sleep, refusal to go outdoors, and self-experimentation... it seems to be an inevitable result. He seems to like cats. He isn't very fond of his family and, in fact, tends to be afraid of people in general. 18 years old, 179cm / 63kg male. (20 years old in Korean age.)