Iwata is a minor villain in the manga Riki-Oh.
A member of the Oowada gang, Iwata enjoys beating up weak people, especially Wakamatsu, an innocent, elderly man who was sentenced after accidentally running over and killing a cop while rushing to the hospital because his wife was pregnant. After Iwata destroyed a wooden toy car Wakamastsu made for his son, Wakamatsu charges at Iwata with a blade, but Iwata trips him over and slices Wakamatsu's face with the blade. As Iwata and his men leave, Riki-Oh trips Iwata over and he falls on a fragment of the toy car which had several nails on it, hand and face first.
Wanting revenge for what Riki-Oh did to him, Iwata bribes one of the guards to release Bando to kill Riki-Oh. However, Riki-Oh easily kills Bando and Iwata tries to stab Riki-Oh with a long needle, but Riki-Oh blocks it and crushes Iwata's hand, and Riki-Oh proceeds to punch Iwata's ribcage out, killing him.
- He is known as Samuel in The Story of Ricky. Additionally, he was also the captain of the guards of the prison, rather than a gang member.