Parasite Monster

Parasite Monster are parasites that takes control of a person's mind.

Overview
Parasite Monsters are created by Doctor. They are developed to reside inside the host’s brain, allowing them to collect the host’s memory data and analyze them, and have a really strong control on the host's mind. The Parasite Monsters are programmed to make their hosts become loyal to Professor. As seen with Serena, Rin and Ruri Kurosaki, the parasite monsters can make their hosts act as sleeper agents, allowing them to retain their normal personalities until the time is right. As seen with Ruri, the true nature of the parasite is to suppress the original personality of that person so that they lose control of their bodies and most of their consciousness. If there is a strong enough external stimulus, it is possible for the host to break free of the parasite temporarily. According to Edo Phoenix the host will be completely free from the influence of parasite when Doctor is defeated. Defeating the host will not free them from the Parasite's control, whether or not their "Parasite Fusioner" cards were destroyed during the Duel or if the host broke free momentarily. Doctor later put a Parasite into a Academia student. The student was asked by Yūya, as to where Yuzu was. The student gave directions and smiled sadistically after Yūya left. Parasite Monsters are also able to quietly enter a host, as shown when one entered through Yūya's ear during his Duel with Serena and Ruri. At this point, however, it was also shown the Parasites can be repelled, as it invoked Yūya's awakening for a moment, which immediately neutralized it.

Those who are under control

 * Serena
 * Rin
 * Ruri Kurosaki
 * Unnamed Academia Student
 * Yuzu Hīragi