Complex sentence: Senkawa were set to meet up with Meiwa Daiichi after two opponents in the Koshien tournament, a fight between rivals, Hiro and Hideo, except that Senkawa loses in the second round to Mitatako.
Split into simpler sentences: Senkawa were set to meet up with Meiwa Daiichi after two opponents in the Koshien tournament. It would have been a fight between rivals, Hiro and Hideo, except that Senkawa lost in the second round to Mitatako.