Also known as: いつか天魔の黒ウサギ
A light novel series by Takaya Kagami, with illustrations by Kamiya Yuu. Also adapted into a 2011 anime by Zexcs and four manga series.
- Serialized in Fujimi Shobou's Monthly Dragon Age, with illustrations by Asahina Shiori
- Serialized in Kadokawa's Shounen Ace, with illustrations by Imada Hidfehito
- Spin-off manga serialized in Kadokawa's Comp Ace, with illustrations by Edoya Pochi
- 4koma manga serialized Fujimi Shobou's Monthly Dragon Age, with illustrations by Tani Takeshi