He could be heard saying: “Aww, I love you. I love you so much,” to AJ.
During spin-off show Strictly – It Takes Two, host and former professional dancer Janette Manrara quizzed the couple on the moment.
“Do you find that you’re getting a bit of a deeper connection in this partnership?” she asked.
Kai replied: “I think that was all down to just the tough, tough week that we had and the fact that we got to the end of the performance and it was flawless and you smashed it, and you did all the lifts brilliant, did all the technique perfect.”
Strictly Come Dancing continues on Saturday at 6.45pm on BBC One.