Dragon Ball Kai

Goku arrives in the Sacred World of the Kais, where Gohan is training with the Z-Sword. Goku decides to help Gohan with his training. Meanwhile, Majin Buu has already killed two thirds of Earth's population. He comes across a blind young boy and heals his vision. Majin Buu becomes surprised when he thanks him instead of being afraid. With Gohan growing more proficient with the Z-Sword, Goku tests out the sword's sharpness by throwing a metal cube at it. Gohan inadvertently breaks the sword in half instead. From the broken sword emerges the Supreme Kai of fifteen generations ago, Old Kai.