Seta Kaoru is a second-year student at Haneoka Girls' High School and the guitarist of Hello, Happy World!. She is very popular with ladies, whom she dubs her "little kittens". Himari and Rimi in particular have a tendency of blushing in her presence.
Outside of the band, she is also Chisato's childhood friend, and their parents are good friends as well.
In the second season of the anime, she is a third-year student.
Kaoru is a tall girl with angular facial features, slanted crimson eyes and long purple hair worn in a ponytail. She has chest length forelocks and bangs that frame her face with a single lock that hangs loose between her eyes.
Her casual attire is normally boyish and formal.
A flamboyant actress, Kaoru has an extravagant personality. She is rather pretentious and bombastic, having a tendency to use impressive sounding words to the point of sounding foreign and hard to understand. She sees herself as a prince, and sees other girls as the princess while quoting Shakespeare or other philosophers (sometimes incorrectly). She appears highly flirtatious, and is very popular among other girls, not only for her passionate mannerisms, but because she is also surprisingly reliable. If she is aware someone may be in a bad mood or feels sad, she will try to encourage them or help them feel better.
When by herself, her "quirks" seem to lessen, if not vanish entirely at times. She appears to be aware of how she can come off to others; sometimes she struggles to have time to herself due to having so many fans, and is aware that she likes certain things that don't fit her "character". She is even able to increase her actress personality if she feels it is necessary.
Though she appears very intelligent, she can often be just as airheaded as Kokoro and Hagumi - such as shown in Little Smiley Steps! where she kept calling the penguin a "little kitten", or thinking that Nietzsche is a woman. Her catchphrase is "fleeting" - though when Hagumi or Kokoro questioned her about what it meant, Kaoru could not answer.
A list of characters Kaoru interacts with in the game.
- Kaoru is part of her high school drama club with Maya.
- Kaoru's theatrical, princely, and flirty personality is a rather open parody of the anime otokoyaku, that is, the anime and manga heroines, inspired by playing male characters actresses from the all-female Takarazuka Theater. It is also emphasized by her close friendship with the very feminine Chisato, who can be compared to musumeyaku, actresses who perform female roles in the same theater.
- This also justifies her popularity with other girls, because Otokoyaku is embodied by the metaphorical image of the "ideal man" who can be simultaneously considered as a charming handsome prince and a reliable female friend who understands women's experiences.
- Kaoru used to call Chisato "Chi-chan" when they were younger and is actually really embarrassed about that.
- In return, Chisato calls her "Kao-chan". Kaoru gets flustered whenever Chisato calls her by that nickname.
- She is both the tallest member of Hello, Happy World! and tallest of all the 25 girls.
- Although Kaoru herself hardly uses word in this sense, in the original Japanese version, “kittens” are a rather obvious pun, as this word is used in Japanese queer slang to refer to the "passive" side in a lesbian relationship.
- Kaoru is scared of both heights and scary things.
- Kaoru is always the one who finds Kanon whenever she gets lost.
- In the game, she mentions she plays sports and swimming and fencing are her favorites.