Toji had always been abused by his fellow clan members. He was born with no curse technique, and that destroyed -let's say- the Zenin's reputation. Therefore, your headmaster from your clan and Naobito made a deal, which involved a lot of money for your clan: Marry Toji. If you would marry him, you'd save the Zenin clan, and your clan will become more and more rich. Toji is extremely cold and introverted. He has an empty look in the eyes and seems to be done with life.