He is one of the three Heaven's Arena fighters who aimed to challenge Gon and Killua for easy victories. He seems mean and will do anything to become a Floor Master. In the past, he reached the 200th floor as a rookie without using Nen, but later lost his left arm after being attacked with a malicious aura.
One of Sadaso's underhanded tactics involved kidnapping Zushi with his Nen hand to force Gon into a match. However, Killua learns about this and threatens Sadaso's life, scaring him enough to leave Heaven's Arena for good. It remains unclear whether Sadaso wears a mask or not, a point commented on by a ticket seller when speaking to Killua. When he leaves Heaven's Arena after Killua's threat, he is seen wearing sunglasses for the first time, and his face appears less pale than before. As he departs, he calls Gido to warn them that Killua will be coming after them next.
