Disclaimer: I do not own Yu-Gi-Oh or any of its characters.
Kaiba hated being proven wrong. It was a rare occurance in and of itself, but he absolutely loathed it.
The one person who proved him wrong the most was a certain Yugi Mutou.
The first time was simple. Kaiba had been called on to answer a math problem in class. Looking up (disdainfully) from his book, he threw out an answer that was close to the right one. Yugi, in his annoyingly innocent way, had corrected him. Strike one.
Second time, not as easily brushed off. During a duel with another student, Kaiba drew the card that he was sure would win him the game. Yugi, appearing with his group of idiots, said as quietly as he could to Kaiba that the card could not be summoned without sending three monsters of a higher attack to the graveyard. The CEO only had one. Strike two.
The third time caused a monumental change in the lives of both young men. Kaiba, talking Mokuba on the phone in the back of the school library, insisted that no one except for his younger brother could love him. When he hung up, Yugi stepped out from behind the shelf next to him and smiled.