The Mirror Card has the ability to reflect and take the form of a chosen person, becoming a 'mirror image' of them. It can also become a mirror and reflect incoming attacks. At first glance, Mirror seems like a tricky, mischievious card, but it is only lost and scared. It is one of the most human Clow/Sakura Cards, not only by having a humanoid shape, but by expressing emotions, speaking, and eating while imitating a person. It has a special condition to be captured, which is that the person must know its name. Mirror also has developed feelings for Touya during their interactions when it takes Sakura's place. Touya treats the card like an individual, since he can tell that it is not Sakura due to his heightened magical sense. The main body of The Mirror looks like a pre-teen girl with long, light green hair, wearing priestess robes, carrying a mirror, and has an emblem on its forehead. It is under The Earthy
The Mirror Card first appears in Episode 25. From the beginning of the episode, Sakura's classmates had been blaming her for various things that have happening throughout Tomoeda. They all claimed the actually saw 'Sakura' commit these pranks, such as Chiharu and Yamazaki asking if she knocked over a store display and then later when Naoko and Chiharu stating she knocked over stuff at a stationary store. Later, Kero taught Sakura how to use the Clow Cards for fortune telling purposes and searched for the truth about the card that took the form of Sakura. The cards were: The Windy, meaning all of the other Clow Cards knew about Sakura, her friends and her family; The Sword when she asked about The Shadow's motives for attacking her, meaning it was testing her; and The Illusion, The Watery and The Shadow defined the card's qualities. The last card was The Flower, which would show present danger. Sakura immediately knew it was Touya as the kanji in his name means "Peach Blossom", a type of flower. And true to the divination, The Mirror led Touya off the edge of a cliff a little while after. The Mirror, in the form of Sakura, checked on Touya, who asked if it could find what it was looking for, since he thought it was a ghost and once it was at peace, it would stop using Sakura's face. He continued by saying he knew that a The Mirror wasn't his sister from the start and then lost conciousness. With the help on Syaoran, Sakura found her brother and confronted the card. The Mirror, now more sombre due to guilt, helps Sakura figure out its name by mimicking her movements. Soon, Sakura pieced it together: "Like a shadow that mimics your moves. Like water that reflects your image. Not real, but an illusion. You are The Mirror Card!". Since it was found out, it reverted to its true form, told the unconcious Touya "I'm sorry", and allowed Sakura to capture it. It appears now and again throughout the series as Sakura's double when she had to distract Touya or her father.
The Mirror Card is transformed into a Sakura/Star Card in Episode 61. Sakura used The Mirror to replace her, yet again, when she left to fight a pair of magicked fence bars. Touya knew that it was The Mirror (or a spirit) was imitating Sakura, but carried on as normal, taking it out shopping. While they were out, Touya bought Mirror a pair of ribbons as a christmas present since he knew the actual spirit of The Mirror Card had long hair. When Mirror returned to its card form, Sakura noticed it was wearing ribbons, not knowing where they came from or how it obtained them.
CCS Manga- Volume 3, Pages 10-75