Remember that time Kyoya Won And Tamaki Lost and he didn't know how to emotionally handle it? Because Tamaki, in essence, was the only person Kyoya never allowed himself to one-up. But he did.
And how even though he won, he still felt like he lost because he used manipulative tactics, compared to Tamaki’s honest way of going about things. He was taught people existed to be taken advantage of, so I think in the end he felt a little guilty, as Tamaki had been the one person he came across in his life who was a true friend. Tamaki wasn’t mad that he lost, and when he explained to him the reasoning behind why he wanted to do this whole activity festival in the first place (he wanted him to participate in a profitless “naive youth fight”, where he was passionate about winning simply for himself), I think it touched/shocked him.
