Dr. Katsuko is the psychologist Ritsuka Aoyagi sees once a week. Her first name is currently unknown, though she is mostly referred to simply by the term "sensei" anyway. She is 21 years old, and genuinely interested in what Ritsuka has to say, being friendly and offering advice and support when needed. Katsuko is troubled by the knowledge that Ritsuka’s mother Misaki abuses him, but is advised by her colleagues not to get involved. Her role in the anime was larger than her role in the manga, in which she has only appeared in the first two volumes.
At times, she seems to flirt with Ritsuka, asking him out on a date in Episode 6 after a deep conversation about life and memories. Whilst on the date she also appears jealous; Ritsuka states he’d eaten some burdock root pasta with friends the other day and upon hearing one of them was a girl, Katsuko mutters “a rival” under her breath. She has told him numerous times that that she likes him a lot though, possibly to reinforce the idea that despite what his mother says, she believes Ritsuka is fine the way he is and wants him to realize it too.
In episode 11, she is seen snapping a pen in two after Kio Kaidou tells her that he saw Yuiko and Ritsuka kissing on a Ferris Wheel (though this is a mistaken observation) and she appears relieved when Ritsuka later explains what actually happened, confusing him with her reaction.
- In the manga, bold hints about her feelings for Ritsuka are not present.
- According to the official English translation) she says about Ritsuka: "If I was twenty years younger I'd have made a move on him".