Iori is Erika's older brother, and is the student council president. Just like his sister, he too is a vampire. He gives off the air of a male model, and has had many girls in his school want to go out with him. He is generally popular with everyone in his school.
Later in manga he reveals that it was his plan to make Erika and Kohei fall in love with each other.
He tells that when he saw the reaction made by Erika when she meets and tries to shake hands with Kohei, he understood clearly that Erika is attracted to Kohei's blood for the reason that Kohei's blood is different or special than other humans.
He made Kohei forcefully join the student council so he could make him get closer to Erika. His plan was to make Erika to make Kohei her servant as she is attracted to only his blood.
When he is offered by his mother to live as a normal human, he decides to not yet do it because he has somethings to take care of.