This is a tribute to the 47 Ronin! There is definitely no way that I could pass up such a classic battle! Kai may have some mystical abilities, but they wouldn’t do anything against a master swordsman like Kenshin. Kenshin doesn’t need any fancy abilities to defeat Kai and a plain slash will suffice. Kenshin is faster and stronger than Kai while still being a cooler character. Kenshin wins.