Carl Clover

Interestingly enough, one of the “Teach me Dr. Litchi” episodes reveals that Carl’s glasses are what gives him the ability to talk to Nirvana, as well as mailboxes and telephone booths. It seems that Valkenhayn has some history with Nirvana, as he is able to talk to and understand her just as Carl is. During a conversation, Nirvana tries to attack him but he mentions that they “are not enemies anymore” and manages to persuade her to calm down.