- "You watch too much anime."
- ―Kagami to Konata
Kagami's physique is average. She has long, light purple hair tied into twin tails with brown ribbons. Unlike Tsukasa, she has sharp violet-blue eyes. She seems flat-chested, like most of the Lucky Star characters, although she is not.
Kagami is the Tsundere in the group and a stereotypical tsukkomi character. She's a bit egotistical, and somewhat weak in common household chores, such as cooking and cleaning, unlike her sister Tsukasa, who excels at cooking.
She can be the straight and intolerant type. However, she is prone to become shy and lonely at times. Kagami is constantly attempting to hide the fact that she has a deep sense of attachment to her friends, especially Konata.
She really does care about Konata, and is almost always willing to go places or do favors for her. Despite this, she seems to take a twisted delight in mocking Konata's smaller-than-average physique, her lack of motivation and her tendency to be a troublemaker, which usually results in Konata becoming very defensive. Kagami is usually annoyed by Konata's constant references to her otaku interests, but usually has an idea on what she is saying. Kagami is always talking about losing unwanted weight, but once she loses a few kilograms she always seems to gain them back again in the blink of an eye because of her eating habits.
Konata always seems to make a joke out of it as well by offering Kagami a pocky stick or teasing her by saying her internal food alarm clock is broken. Kagami likes reading light novels unlike Konata, who is always reading manga. Kagami is a very good team leader and likes to get things done.
Kagami is Tsukasa's older twin sister and is occasionally referred to as "Kagamin" by Konata. In school, her grades are excellent because she studies very hard. When Kagami was in seventh grade she made it into Ryōō High School and was made the class president in her first year. Kagami always seems to be put in the same class as Misao Kusakabe, and Ayano Minegishi. She has been in the same class as those two since fifth grade. She is always in a different class than Konata and Tsukasa, but she frequently comes to their class during lunch time to eat with them, to the point where she is on a given name basis with their class but not with her own classmates. Kagami is often shown wishing she could be in the same class as Konata. Kagami chose the humanities course in her second year so that she could be with her, but she was separated into a different classroom. She is also the 2nd youngest member of the Hiiragi family, the other one being her twin sister, Tsukasa, who is the 1st youngest member of the family.
Character song Vol. 002 Kagami Hiiragi features 4 songs performed by Kagami's voice actor, Emiri Kato. The songs are:
- Kenka Yoho no Jikan Dayo
- 100%? Nai nai nai
|Konata Izumi - Tsukasa Hiiragi - Miyuki Takara - Kagami Hiiragi - Ayano Minegishi - Misao Kusakabe - Yutaka Kobayakawa - Minami Iwasaki - Hiyori Tamura - Patricia Martin - List of Characters|
|Sōjirō Izumi - Kanata Izumi - Yui Narumi - Tadao Hiiragi - Miki Hiiragi - Matsuri Hiiragi - Inori Hiiragi - Yukari Takara - Honoka Iwasaki - Nanako Kuroi - Hikaru Sakuraba - Hinata Miyakawa - Hikage Miyakawa - Akira Kogami|
|Goldy - Cherry|
|Anime Only Characters|
|Minoru Shiraishi - Meito Anizawa - Daisuke Ono - Gotouza|
|Manga Only Characters|
|Kō Yasaka - Yamato Nagamori - Izumi Wakase - Fuyuki Amahara - Tamaki Yamanobe - Miku Busujima|
- In Japanese,"Kagami" means "mirror". She was named so because in the Shinto religion, mirrors are believed to attract the gods' favor, and because old fashioned mirrors are round, and resemble a well-rounded family.
- Unlike some other characters, Kagami, like her sister, is left handed.
- In episode 18, when Konata and her friends play the animal personality game, Kagami thinks that Konata would say that she would be a tiger or a wolf, but, instead, Konata says that Kagami would be a rabbit because she's lonely, and that her twin tails look like rabbit ears.
- Kagami is the last main character to be introduced, since she does not appear until the second chapter of the manga.
- Kagami was also the winner of 2channel's 2008 Saimoe Tournament.
- In the anime, Kagami's favorite color is black, while in the manga (Volume 4), it is violet.
- Kagami has the same first name as the creator of Lucky Star, Kagami Yoshimizu, while her sister shares the creator's pen name, Tsukasa Suina.
- In the OVA episode, Kagami says "I want to ***** with Konata" while half asleep. The censored word is presumed to be "sleep", which could be the reason why the former appears greatly embarrassed when her sister, Tsukasa, hears it.