A mouse (走狗(マウス), Souku, lit.,"tool") is an entity that a person uses in conjunction with the usage of an ability. They mostly come in small human- or animal-like forms and their functions vary on the ability user.
- Hanami (used by Tomo Asama)
- Michizane (used by Toussaint Neshinbara)
- Uzzi (used by Kimi Aoi)
- Erimaki (used by Shirojiro Bertoni and Heidi Augesvarer)
- Tsukinowa (used by Masazumi Honda)
- F. Walsingham
- Matsu (used by Toshiie Maeda)