Failure
Sora has always been a strong-willed person at heart, he hated how failure felt and sought to do his best in any and every situation. He had very high expectations of himself and decided that it would feel like failing in itself if he didn't, so he made sure to get the best possible outcome out of everything and also try his hardest to help his friends in their own time of need.
But when he arrived at Twilight Town and heard of Kairi's kidnapping, no other feeling could compare to the heaviness of letting his dearest friend down or the strongest sense of failure ever felt by the young man.
They would accompany him until he could hold her safely in his arms again.