The Night Guy is a forbidden taijutsu of the highest level, that takes the shape of a dragon, and can only be performed by opening all Eight Gates.
When Guy initiates the technique, he emits an enormous amount of chakra. After gathering all of this chakra around his body, the blood vapour of the Eighth Gate manifests into a red, flickering dragon-like aura. He then dashes forward at such an extreme speed that the space within the immediate vicinity of the technique is distorted, making it impossible for the target to defend against it. Guy then deals an immensely powerful kick which carries such force that it is capable of obliterating the target's body, as well as creating a devastating shock wave linear to the kick. The damage itself was so great that even Madara Uchiha as the Ten-Tails' jinchūriki thought he was going to die.
The recoil was such that it completely shattered the bones in Guy's own leg. As a result of being Guy's strongest manoeuvre, following the attack are fatal repercussions as it left Guy on the brink of death; slowly turning into ash, crumbling from the immense discharge of his chakra.
Because of Night Guy's effects, even after Naruto Uzumaki's use of Yin–Yang Release to restore Guy, the taijutsu master remained permanently disabled, confined to a wheelchair for the rest of his life.