As a young boy, Krillin studied martial arts with Goku under Master Roshi. Originally he and Goku were fierce rivals, but now they've become the best of friends. Krillin soon realized that Goku was special and that the Power of Light was very strong within him, and he now holds Goku in high respect. But don't get the idea that he's a helpless buffoon. A good fighter in his own accord, he's always there to help Goku. He can and has saved his friend's life more than once. In fact, Krillin unleashes an incredible energy blast shaped like a flying disk that literally slices through mountaintops. Krillin is incredibly dedicated to his friends, especially Goku, and holds friendship in high value. He is willing to fight against the Saibaimen and Saiyans even though he doesn't want to die and knows he can't be brought back to life again by the Dragon Balls. Goku constantly encourages Krillin to have confidence in his own abilities as Krillin learns to be a remarkable fighter--that is, for an earthling.
Krillin later, falls in love and marries Android 18. Both participate in the World Fighting Tournament.