I think they brought Kiyoharu in as a fresh character for future "adventures".
But I think they did realize that future stories, because of the absence of the odd character, namely Sai, can only be variations on the tournament theme. (unless they want to do personal stuff, which they've never done before) And that would be boring the Nth time around.

Touya sr. showing up is a good way to round off the story, after all he's Sai's true rival, even though they only played the one even game...