1. Kagetane appears to be Catholic.
2. Kisara’s grandfather is actually the grand mastermind behind Kagetane’s attack. (This was alluded to in the anime)
3. Kagetane called Rentaro after his supposed death, and told him he was still alive. So Rentaro knew that he would have to fight him again.
4. Seitenshi is still high school age, and goes to the same school as Kisara. Seitenshi is a title.