Iwamoto

Iwamoto is vindictive, dishonest and strongly prejudiced against students he considers delinquents. Rather than judging Yusuke and Kazuma Kuwabara on individual incidents, he assumes the worst about them and is prepared to manipulate circumstances to justify punishment.

His behavior contrasts with teachers such as Takenaka, who recognizes that Yusuke has serious behavioral problems but still treats him as a student worth helping. Iwamoto instead uses his authority to antagonize him.

Iwamoto is an ordinary human and has no natural spiritual or supernatural powers.

During the Four Saint Beasts storyline, a Makai Insect possesses him. The parasite makes its human host violently responsive to the Makai Whistle controlled by Suzaku, temporarily turning Iwamoto into one of the possessed humans hunting Keiko.

Earlier, Iwamoto inadvertently serves as the target for Yusuke's first practical test of the Spirit Gun. The attack demonstrates that Yusuke's newly acquired technique can physically affect a living human.

Iwamoto appears during Yusuke's early school life as one of the teachers actively trying to have him expelled. He and Akashi exploit the reputations of Yusuke and Kuwabara's group, providing a mundane form of opposition alongside the supernatural cases Yusuke begins handling.

Yusuke later tests his newly learned Spirit Gun by firing it at Iwamoto, knocking him unconscious.

During the Four Saint Beasts crisis, Iwamoto becomes infected by a Makai Insect and, under Suzaku's influence, pursues Keiko Yukimura through Sarayashiki Junior High. When Yusuke destroys the Makai Whistle, the insect controlling Iwamoto dies and he returns to normal.

Yusuke Urameshi is the student Iwamoto most openly dislikes and repeatedly attempts to punish.

Akashi is a fellow teacher who shares Iwamoto's hostility toward Yusuke and his friends.

Takenaka takes a considerably fairer approach toward Yusuke than Iwamoto does.

Keiko Yukimura is pursued by Iwamoto while he is under the control of a Makai Insect.

Suzaku indirectly controls the possessed Iwamoto through the Makai Whistle.