A group mainly composed of Hybrid Yōkai, half-breed monsters that take no definitive, physical form of anything classified as a supernatural creature (such as a Vampire or a Werewolf), who wish for nothing more than to destroy the current school system. They have an extreme hatred of pure-blooded yōkai, who they claim look down on half-breeds, forcing them to become subservient to their pure-blooded masters while Hokuto (the leader) wants revenge against Yokai Academy for forcing him to become a yokai in order to survive. In the localized manga, they are referred to as "Monstrels". While they were once lead by Hokuto Kaneshiro, it is clear that ANTI-THESIS is not affiliated with Fairy Tale as some members were seen fighting the Alucard's clones in the final battle.
Most members of ANTI-THESIS do not appear in the anime adaptation, as the anime focuses more on the aspect of the series. (In other words, the organization is manga-exclusive). Members of ANTI-THESIS are typically antagonists and also called "Anti-Schoolers" (反学派 Han Gakuha) or one being known as an "Anti-Schooler" in English singular.
ANTI-THESIS hideout