Sensui was born with a natural talent for sensing and destroying demons. His black and white view of the world and desire for justice made him a perfect candidate to became a spirit detective, and he quickly adapted to the job. Throughout his job as Spirit Detective, Sensui was partnered with Itsuki, much in the same capacitiy as Botan is to Yusuke. Sensui took on a rather simplistic view; humans are good and should be protected, while demons are evil and must be killed. However, this was turned upside down when he witnessed the Black Black Club torturing demons for sheer joy. Confused about the true nature of humans, Sensui stole the Chapter Black tape from Spirit World and fled to the Human World. With Itsuki, the two would assemble a team of seven psychics that was intended to help bring an end to the human race.