Convincing Riven to open up her bloody and painful past would be difficult enough, but if you add to the mix that it's Yasuo who wants her to open up, the challenge becomes insurmountable, not to mention highly dangerous. The Exile will respond to his early attempts with combat and violence, though with enough finesse he can sidestep her aggression and get what he wants: Information. Doesn't mean he won't get more, though.