John had left after a while, telling Kai that he needed to rest and think about things. The prince had greeted him, trying not to show how worried he was. He had hoped his words had put some sense into him. When he heard him say that he tried to kill himself he couldn't help but think of himself, how helpless he felt when he let Philip bit him.
John's pain, he could understand it to some extent, thinking how you could never have the one you wanted, being scared to show your feelings. Indeed it was torture and he never wished that for anyone, not even his worst enemy. He wanted to check up on him later and that's why he rushed to the throne room, wanting this whole conversation he had promised to his father to be over.