Tanaka has an eccentric and somewhat dark personality. He often claims that he has been blessed with the evil powers of the underworld, and refers to everyone else as 'pathetic human beings'. Tanaka is often lost in his own little world, usually paying more attention to himself or his hamsters than the things that are going on around him, such as in Chapter 1 when he failed to investigate after the murder and putting his lost Hell Hound Earring at a higher priority. He may also have an interest or knowledge of alchemy.

Despite first impressions, Tanaka is generally rather comical in what he says to Danganronpa spectators (not so much for characters actually talking to him), and somewhat contradicting or counterproductive: such as in his introduction, when he tells Hajime Hinata to step forward and introduce himself, for Tanaka will destroy him once he does. He also constantly tells others not to come near him or to touch him, claiming that poison runs in his veins.

However, despite his 'I am the Dark Lord' ramblings, Tanaka is shown that he seriously cares about animals, and understands them much better than he understands people. In one of his Free-Time Events, he tells Hajime that he runs an informational website about breeding which he maintains carefully. It is also implied that though he puts on the face of a loner who wouldn't dream of hanging out with pathetic mortals, Tanaka actually may be very lonely as he once boasted that he was searching for solitude before wandering away slowly and silently.