In the final test of the Hunter Exam, Hanzo is forced to battle Gon. His speed, strength, and battle experience easily exceed that of Gon. However, the only way to pass the final test to is force your opponent to admit defeat--Gon refuses to do so even after being severely beaten. Hanzo breaks Gon's arm to force him to admit defeat, but Gon still refuses. Noting the lack of hate in Gon's eyes after this act, Hanzo realizes he actually has come to like Gon. He willingly bows out of the battle, giving Gon the victory needed for him to pass the final test. Hanzo was examinee #294 during the 287th Hunter Exam.
It is later stated by Wing that Hanzo learned Nen after the Hunter Exam, though he has yet to reappear in the series.