The Fire Rasengaan is an incredible jutsu that Naruto Uzumaki Jr. learned. He learned the Rasengan from his father and Kakashi taught him how to control his chakra control. Naruto Jr. combined how he learned chakra control and the rasengan from Naruto and created the Fire Rasengan. The Fire Rasengan can also be used by Naruto Sr. in his Kyuubi form and the jutsu can kill one with Water Type chakra. The Fire Rasengan is equal to the Lightning Rasengan.