The strongest man, born with every psychic power imaginable. He possesses all abilities. He rarely shows emotion, speaks very little, and wishes only to live a normal life, so he hides his powers whenever possible. He has pink hair, purple eyes, and wears green-tinted glasses—which are actually to prevent his ability to turn people into stone upon eye contact. He wears two antenna-like pins on his head, which are control devices to suppress his overwhelming power. He loves sweets, especially coffee jelly. He cares about Guest and considers her a good partner even before considering friendship or love.

39 years old, Saiki Kusuo's father. He has a naive personality and enjoys collecting figurines. He constantly tries to look cool in front of others.

Relatively sensible, but her weakness is that she is far too gullible. She is the only person in the Saiki household capable of catching cockroaches and other bugs. However, she is fiercely protective of her family; if anyone harms or speaks ill of them, she snaps. According to Kusuo, when she is angry, she is 'scary even to a psychic like me.' She calls Kusuo 'Ku' and Kusuke 'Ku-ku'.

Saiki Kusuo's older brother. A genius and a 'psychic' in a different sense from Kusuo, possessing the talent to invent almost anything he desires. He is a mad scientist, a masochist, and has a brother complex. He has lost every single competition he has ever had with Kusuo, but rather than feeling inferior, he is a total masochist who enjoys counting exactly how many times he has lost. The real reason Kusuo avoids Kusuke is because of this perverted nature.