He couldn't picture sharing this with anyone else.
They stand tall and proud on the stage together, him the first to volunteer and her willingly Reaped. They make an excellent team, five years of training side by side has slowly formed an excellent bond - one that can't be broken by bickering and mindless insults. The thought of killing her, stupidly, doesn't even cross his mind as he pictures riding chariots together and having matching training scores.
He's brought back to earth by her shaking his hand, and promising to crush him. He scoffs - "You're crazy."