Thread:GunBlazer/@comment-205.152.72.99-20140128152314/@comment-26168276-20140128162647

Terumi's vessel has its own mind. In Phase Shift 1 Terumi merged with Kazuma, and their minds became one. When Nine placed Mind Eater spell on Terumi, he separated his mind from Kazuma's, so only Terumi was affected. Kazuma then acted like Terumi, and pretended to be under Nine's control. Later Trinity released Terumi from Mind Eater, but spell left a side-effect: Terumi can't merge his mind with vessel's mind. So it's like two (very similar) personalities in one body.

In CP, Trinity did some magic on them, so Hazama and Terumi became separated as two different persons.