The two of them also share a much darker, sadistic side to their usual playfulness. As shown in the manga and light novels, the two of them seem to enjoy torturing people and inflicting pain on others. The methods they use usually follow a theme representing a manga they force their victim to choose (this aspect of them is hinted at in the anime but is much more toned down). It is unknown exactly how they developed this kind of personality although it is implied by Erika that they used to work for various illegal organizations before Kyohei (as Erika puts it) "Pulled them out of the darkness" which implies that Kyohei was responisble for reforming them back to regular society.

Although the two of them are extremely close, it is shown in the light novels that Walker is slightly more attached to Erika than she is to him. Whenever Erika temporarily leaves to go hang out with her cosplay group or with another friend outside of her usual group, Walker is shown to be extremely depressed and bored since there is no one else he knows that likes anime and manga (at least no to the extent he and Erika do).

Erika, on the other hand, appears to be the more independant one between the two of them as well as the more responsible one. This is most evident during episode 19 of the anime when, after Masaomi was asking about the blue squares, Walker nearly loses his temper but Erika manages to calm him down. She also appears to be more social than Walker as she has numerous friends outside of the Kyohei's group whereas Walker is only ever seen with either Kyohei or Saburo when Erika isn't around.