Kotoko is far more serious than Sumomo, and thinks that everyone in the Motosuwa household is crazy, Sumomo in particular. Kotoko's speciality is research, which twice drives the story forward. Kotoko is also programmed to always tell the truth, no matter what, even when it works to her owner's disadvantage. She is serious and cynical, except when researching something, to the point of being tsundere.
Voiced by: Yukana Nogami (Japanese), Kari Wahlgren (English)