A Guardian Character with an artistic flair. A cool, quiet character. Her hairstyle is a short bob cut. She usually wears a pair of half-cut pants, a sky blue beret with a spade on it, and a blue themed outfit. Miki has shown an interest in both Tadase's Character, Kiseki, and Ikuto's Character, Yoru. She comments that Yoru is cool and his tail is cute. This may imply the situation in Amu's heart.
In the anime, she is also shown to like Musashi, Kairi's Chara. Though Amu doesn't love Kairi herself, he does have a crush on her.
The main ability after Character Change is an increased artistic sense but that power is recklessly abused.
Amu becomes "Amulet Spade" when she Character Transforms with Miki. The clover decoration of her Humpty Lock changes to the color blue. Amu wears a white frilly blouse with a pair of light blue pants. She also wears long, striped stockings and a garter belt; all in a blue themed costume. Her special move is "Colorful Canvas," where she paints with a giant paintbrush. Miki says "Drew, Draw, Drawn" during a Character Transformation with Amu.
When first introduced, Miki saw that Amu was yelling at Ran (First hatched Guardian) so that she could leave her life. Miki ran away being scared by Amus outburst. Miki was later found out to be Amus spade guardian. Miki is shy, yet also out-going at the same time.