The reduced color palette was applauded for highlighting the sense of "mental disease" and "emotional malaise" that affected most of the characters, while the vignette effect allowed the viewer to observe inside the series rather than just watch it. Character designs have been criticized as "bland" but also "realistic" since none of the characters have "outrageous hair styles or colors". Reviews also recognized that "astute viewers may notice some rather interesting, although not very blatant, differences between the various characters", and that the "realistic" character designs created a degree of "normalcy" that was important to the story while also helping to draw in the viewer. The audio of the series has been described as "unique" and "incredible", going beyond what is expected of normal sound design and enhancing the "creepy" atmosphere of the show. Also noted was that the opening and ending songs don't appear to fit in well with the mood of the series. The English language track was not as well received as its Japanese counterpart, but still reviewed favorably. In particular, the performance of Jessica Calvello in the English dub was singled out and praised as being her best performance to date.