|Anime Debut||Episode 1|
|Handler:||Toru Kitsutaka (Ex-Handler)|
|Burial Doll(s)|| Aki Kitsutaka (Ex-Burial Doll)
- Natsume Tomoharu
- Toru Kitsutaka (EX)
- Misao Minakami
- Aki Kitsutaka (EX)
A dark Asura Machina that emerged from the Extractor at the end of the first episode in a wave of shadow. It was given to Tomoharu during the the plane crash by Naotaka when Misao volunteered to be a Burial Doll to save Tomoharu. However, apparently after having made the contract Kurogane's Extractor fell into the hands of Toru, who became the first Handler of Kurogane. Kurogane's gravity control ability manifests itself as balls of dark energy, though it also has the ability to engulf its hands with energy to strengthen its physical attacks. In the anime Kurogane's gravity control is so great that it is able to overcome Rhodonite's time manipulation. In order to save the vanishing First World, Tomoharu asks Ania to use her abilities to fuse the remains of Kurogane and Shirogane in order to try and create a new Asura Machina which could be equal to Hagane, resulting the creation of the Kurogane Kai.