Double (二に倍ばい, Nibai?) was the Quirk used by Jin Bubaigawara. Jin needed a flawless image of whatever he planned to duplicate stored within his mind, so the measurements and physical features had to be extremely accurate. Without a perfect image, all Jin would get was a poorly formed copy that wouldn't last long. Therefore, every time a person undergoes any physical change, Jin had to take the measurements again.