"Episode 20"

Due to his realization that he and his brothers may "not" be able to become "Adam", Ruki begins to act strangely to the extent where he confines Yui in a small room to forcefully suck her blood. As this happens, his brothers grow concerned for him and Yui as she becomes weaker. Ayato takes action abducting Yui to which Ruki offers no resistance much to the confusion of his brothers.