Shadow Rasengan (シャドウ螺旋丸, Shadō Rasengan) is a powerful technique invented by Future Paul Gekko, which he created by observing the Tailed Beast Ball. He spent three years developing the Rasengan; his plan was to take the shape transformation of one's chakra to the "highest possible point" and then combine it with his chakra's nature affinity, creating a technique that did not need the aid of time-consuming hand seals to control. He taught it to Paul Gekko and his Future Children and his Future Wife.
The Rasengan does not require any hand seals to use, relying only on the chakra control of the user. Once it is complete, it becomes self-sustaining, which does not give the Rasengan a definite limit like the Jet Stream Rainbow Bomb. The compacted nature and moving speed of the chakra allows the Rasengan to grind into whatever it comes in contact with to inflict major damage. This tends to launch the target spiralling backward after being hit or, if the target is lying on the ground or being launched to the ground, the destructive force is enough to form a crater. It can unleash the Giant Laser Beam which may result in a explosion similar to a atomic bomb from World War II.
According to Kuro no Mikoto, someone from the Future blocks it's attack to prevent the person from the Present from being weakened.
- The Shadow Rasengan is a Darker Version of the Rasengan.
- Before Two Paul Gekko's Clash, Natsu interrupted Future Paul Gekko's Shadow Rasengan easily.
- Natsu of the Fairy Tail dosen't like the Shadow Rasengan because the Giant Laser would destroy Lucy Heartfilia's Future.
- The Shadow Rasengan in the Christopher Gekko Arc was shown to take a form of the Ion Bullet during OPERATION: C.A.K.E.D-S.A.G.A in Sixth High School War.