|Hair||Ankle Length, Blue, Sidehair, Straight, White|
|Body||Pale, Slim, Small Breast Sizes, Tiny, Wings|
|Clothes||Detached Sleeves, Fingerless Gloves, Hat, Naked, Thigh-high Stockings|
|Role||Commander, Customizable Appearance, Homunculus, Living Doll, Magician|
|Engages in||Fighting, Flying|
|Visual novels||Main character - Madou Koukaku ~Yami no Tsuki Megami wa Doukoku de Utau~|
|Voiced by||Shinozaki Futaba|
Aru is a mechanical doll about 70 centimeters tall and one of "Magical Machine Doll" (Madou Koukaku). She has very sparse emotions and always thinks and acts logically. Out of the four months that exist she represents and takes name after the Moon Goddess Arutanu, governing the "Moon of Darkness". She joins Weiss under certain circumstances, and decides to learn and remember his actions and ideas which come together as his personality.