I attributed The Hero to Naoki namely due to him being the one to form the team and admittedly making an assumption that he'll be the default Captain later on.

Still don't really know what Riku is. Too tough to be a pure Smart Guy, too smart to be the Big Guy. And I think you're right that Kai and Jun suit The Lancer, especially to each other. That doesn't leave Riku with very much, and I sure as hell wouldn't call him The Hero, that's for sure.